Detailed reports of a door-to-door mass killing by pro-government forces in the Syrian countryside emerged on Thursday as unarmed United Nations monitors were blocked and then shot at trying to get to the scene, fueling international condemnation of the government of President Bashar al-Assad.

Reports by the Syrian opposition of the slaughter of at least 78 people, including women and children, in Qubair, a farming hamlet on the outskirts of the embattled central city of Hama cast a chill on a session of the U.N. General Assembly devoted to the Syrian conflict.

Syria´s government rejected the reports. The regime´s news agency SANA, quoting a Hama official, said only nine people were killed in Qubair after it was attacked by an "armed terrorist group" from a nearby village.

Special envoy Kofi Annan expressed "horror and condemnation" at the reports and said "we cannot allow mass killing to become part of everyday reality in Syria."

The White House accused the Syrian government of orchestrating "the outrageous targeted killings of civilians, including women and children," and said the violence shows Mr. Assad "has no credibility and only further underscores the illegitimate and immoral nature of his rule."

There were also unconfirmed activist reports of mass casualties resulting from helicopter gunship attacks on the town of Heffe in the western coastal province of Latakia.

Syria´s U.N. representative, Bashar al-Jaafari, denied the report from Heffe, as well as that from Qubair. "This is exactly what inciting media outlets now routinely broadcast ahead of Security Council and General Assembly meetings," he said.

In echoes of the massacre of 108 people in Houla in western Syria two weeks ago, activists said the victims in Qubair belonged to the country´s Sunni Arab majority while the alleged perpetrators— government special forces, pro-regime militants and residents of surrounding villages—hailed from the ruling Alawite minority.

"These killings are indicative of a pattern of widespread and systematic attacks against civilian populations and may amount to crime[s] against humanity," U.N. Assistant Secretary-General for Human Rights Ivan Simonovic told the General Assembly.

Both Secretary-General Ban Ki-moon and Mr. Annan acknowledged the failure of a six-point peace plan and urged the international community to begin exploring other options.

Mr. Annan told the assembly that he met with Mr. Assad after the Houla massacre and he told him to "radically change his military posture" and implement the peace plan that he had agreed to. "Since then, shelling of cities has intensified," Mr. Annan said. "Government-backed militia seem to have free rein with appalling consequences."

Mr. Annan is exploring an initiative that would include Assad allies Russia and Iran in diplomatic efforts to end the bloodshed in Syria, which the U.N. says has claimed the lives of more than 10,000 people.

Mr. Annan, after addressing the Security Council on Thursday, publicly called for Iran´s participation. But U.S. Ambassador Susan Rice rejected the idea. "I think Iran is part of the problem in Syria," Ms. Rice said.

Also on Thursday, Russia rebuffed calls at the Security Council to move on economic sanctions against Syria.

Reports from Qubair were pieced together through telephone interviews with opposition members, residents and activists. Pro-regime militants known as Shabiha, and residents from Alawite villages near Hama arrived by bus at Qubair at around 2 p.m. Wednesday, accompanied by a contingent of government soldiers in tanks and trucks equipped with antiaircraft guns, the people said.

The village, with 140 inhabitants, was surrounded from three directions, said Maher al-Nuaimi, a defected Syrian army officer who is from the same area.

At first homes in the village were hit with shells and a barrage of gunfire and then pro-regime militants went door to door shooting and stabbing residents and setting some homes on fire, according to two residents of the area. They gave a toll of 86 killed.

Enlarge Image

AFP/Getty Images A handout picture released by the Syrian opposition´s Shaam News Network shows Syrian rebels posing for a picture during the funeral procession of a man killed in violence in Silkin in the northwestern province of Idlib on Wednesday.

Mr. Nuaimi, who gave a toll of 78, said the pro-regime attackers remained in the area until about 9 p.m. He said about 40 bodies, mostly of men, were taken back to the nearby Alawite town of Asilah as trophies.

SANA, the state news agency said residents called in security forces to intervene after terrorists attacked the village, and when they arrived they clashed with the attackers.

More

Annan Pursues Talks on Easing Assad Out After the attackers left, inhabitants of nearby villages rushed in and took out 17 bodies, including six that were badly charred, to a mosque in the region, where they were filmed by local antiregime activists.

The footage, posted on YouTube, couldn´t be independently verified. It shows bodies of children and women lined up on a floor. Some are covered in blankets while others are shrouded in white sheets for burial in accordance with Muslim tradition.

"Is this child a terrorist or an Israeli agent?" asks a male voice on the video as the camera pans on the body of a child.

—Carol E. Lee contributed to this article. (Copyright © Dow Jones & Company, Inc.) 06/08/12)