The U.N. Security Council has blamed Syrian government forces for artillery and tank shelling of residential areas in the town of Houla and it is strongly condemning the killing of dozens of civilians.

The council said in a press statement issued after an emergency meeting Sunday afternoon that it also "condemned the killing of civilians by shooting at close range and by severe physical abuse" in Houla. It did not say who was responsible for the close-range attacks. The U.N. says at least 108 people, including 49 children and 34 women, died in Friday´s attacks in Houla.

The council statement says the "outrageous use of force" against civilians violated international law and Syrian government commitments under Security Council resolutions to cease violence, including the use of heavy weapons in populated areas.

The 12-hour artillery barrage that began on a string of villages northwest of Homs on Friday afternoon—which Syria´s government denied any role in on Sunday—also drew international condemnation and effectively upended a cease-fire most international powers had banked on as the best way out of Syria´s crisis.

Western officials said they were still committed to seeing through the peace plan brokered by Kofi Annan, a joint envoy of the U.N. and Arab League, underscoring the limited scope of viable international action on Syria, even as the violence in the country appeared to spiral again.

"It´s not like there is a range of options out there or alternatives to cease-fire and peaceful transition," a U.N. official said on Sunday, adding, "If or when countries become ready to take alternative action, then I don´t think the mission will be an obstacle."

In a renewed diplomatic push at the U.N. Security Council, Western nations pressed to hold Syria´s government accountable for the attack, one of the single bloodiest incidents of violence in the 14- month uprising against President Bashar al-Assad. Mr. Annan on Saturday called it a "flagrant violation" of both international law and Syria´s commitment to the cease-fire.

The press statement was open to different interpretations by Western council nations on the one hand, and the Russians and Syrians on the other. The disagreement centered on who was responsible for the killings at short range and what the circumstances were leading to the atrocity.

Bashar Jaafari, the Syrian ambassador to the U.N., told reporters that the incident began after Friday prayers when 200 to 300 opposition fighters gathered from several points in Houla with pick- up trucks armed with anti-tank missiles, mortars and machine guns. Mr. Jaafari said they began attacking local police in the town for nine hours on Friday, before moving to burn a hospital and attacked farms and houses in a neighboring village.

While he did not deny that the Syrian army fired tank rounds into a neighborhood of Houla, he said, "These shells would not have killed these innocent civiians who were killed at short range." Mr. Jaafair charged that "armed groups have initiated these kinds of attacks from the beginning of the crisis." He suggested they were carried out in Houla to undermine Mr. Annan´s visit to Damascus on Tuesday as well as to provoke international armed intervention.

"One of the reasons for perpetuating these crimes might be to increase the internationalization of the Syrian crisis," he told reporters. He said those found guilty of the killings would be held accountable by the Syrian government.

Gen. Mood told the Security Council that the circumstances leading to the killings remained "murky," diplomats said. He also said it was impossible to tell how many of the 108 victims were killed by shelling or by close-range gunfire. Many of the bodies could not be examined for forensic evidence because they were either interred or wrapped for burial, diplomats quoted Gen. Mood as saying in his closed-door briefing to the council.

"It does not matter what the circumstances leading up to the atrocity was, it was an atrocity and it was committed by the Syrian government," Mark Lyall Grant, the British ambassador, told reporters. He added that despite the incident, "The Annan plan is not dead but it has not led to what it was supposed to: political dialogue."

German Ambassador Peter Witting told reporters: Gen. Mood and [U.N. peacekeeping chief] Herve Ladsous confirmed today very straightforwardly that there is clear evidence of the use of heavy weapons, shelling, even traces of tanks in that area. So the evidence is clear, it is not murky. There is a clear footprint of the government in the massacre."

Mr. Witting called for a commission of inquiry to look into possible war crimes. Navi Pillay, the U.N. High Commissioner of Human Rights also on Sunday called for an investigation into potential crimes against humanity committed in Houla.

Still, the artillery assault on Houla, which U.N. monitors in Syria confirmed in a field visit, cast deeper doubt over the viability of a peace plan the opposition now appears no longer willing to entertain.

Rage mounted among Syrian protesters on Sunday at what many perceive as the Syrian government´s immunity from punishment.

Activist groups reported government shelling in two towns and fighting with rebel forces in a handful of spots across the country on Sunday.

Rebel fighters vowed to escalate attacks against the regime if the international community didn´t intervene in response to the Houla attacks, as protesters poured into the streets of most major cities for solidarity marches.

The rebel Free Syrian Army said it could no longer commit to the cease-fire. An influential grass-roots group of activists and fighters, the Homs Revolutionary Council, said it would stop meeting with the U.N. mission except on humanitarian issues.

The council called the U.N. monitors "helpless" and accused them of not intervening despite being presented repeated evidence of the regime´s cease-fire violations, "except to count the victims the day after the massacre just as the U.N. did in Sarajevo and Srebrenica in Bosnia."

Angry calls from protesters raised concerns over the safety of the U.N. monitors.

"The Annan mission achieved little successes here and there," said Rim Turkmani, the London-based spokeswoman for an opposition political group in Damascus. "But after the Houla massacre, people are extremely emotional. They don´t want to listen to anyone or anything," said Ms. Turkmani. "It´s a very tough time."

In an apparent response to the outrage, Syria´s Foreign Ministry held a news conference in Damascus on Sunday, acknowledging the Houla attacks as a "massacre" but denying government tanks or artillery were in the vicinity.

Jihad Makdissi, spokesman for the foreign ministry, said hundreds of "heavily armed gunmen carrying machine guns, mortars and antitank missiles" launched a nine-hour barrage from several locations, killing three soldiers and wounding 16 as five army positions came under attack simultaneously.

He said Syria was facing a "tsunami of lies" on the incident, which state television a day earlier blamed on al Qaeda-linked terrorists.

U.N. monitors at the site of the attack said they saw spent artillery amid rubble in residential neighborhoods and counted 92 bodies, including those of 32 children below the age of 10, confirming accounts by witnesses and opposition activists, who put the death toll from the incident at slightly above 100.

"There was not a minute between each rocket and shell," said Ahmed Qassem, a Houla native living in Saudi Arabia who tracked the attacks through his family in the village.

Witnesses and activists said the tank shelling and rocket fire began Friday afternoon. Security forces had fired at protesters marching out of mosques after the Islamic prayer at noon, leading to fighting between opposition and government forces in which, according to two witness accounts, two army officers and several other soldiers were killed.

In apparent retribution, the government started to shell the string of villages in a bombardment that lasted at least 12 hours, these witnesses and other activists said.

Western diplomats said on Sunday they were concerned that the Syrian government would continue to escalate attacks.

But the mission of some 250 unarmed U.N. monitors in Syria is unlikely to change course despite growing questions over its relevance, and new calls for alternative routes of action on Syria.

The mission is part of a broader U.N.-backed peace plan that sees a cease-fire as a starting point to a political transition that would ease President Assad out of power. For months, Western officials have voiced concerns over the plan but said it remains the only viable diplomatic option, one designed to bring Russia—Mr. Assad´s strongest international ally—on board.

"The international community is not agreed on whether there would be intervention or what type of intervention there would be if the Annan plan didn´t work," U.K. Foreign Secretary William Hague said ahead of a visit to Moscow on Sunday.

"Our emphasis for now and the emphasis of all the permanent members of the Security Council—Britain and Russia included—is to try to get the Annan plan to work," he said, adding he hoped Russia would "redouble efforts" to urge Mr. Assad to stick by the plan.

Reports of pro-regime groups from neighboring villages raiding homes and stabbing women and children to death Friday night, after the tank and rocket fire on Houla had stopped—in what some activists described as violent sectarian killings—remained unclear.

Mohammad Abdel Karim al-Moustapha, an activist in Houla, said pro- regime thugs from the Alawite villages neighboring Houla—a plain of largely Sunni towns—began to storm houses at dawn.

"They want to scare us, and drive us away forever," Mr. Moustapha said by telephone.

Other activists disputed those accounts and cautioned against further inflaming sectarian rage between the largely Sunni opposition and members of the Alawite sect, to which Syria´s president and much of the higher ranks of the repressive military and security apparatus belong. —Joe Lauria at the United Nations and Associated Press contributed to this article. (Copyright © Dow Jones & Company, Inc.) 05/28/12)