The Obama administration accused Russia of sending attack helicopters to Damascus, linking Moscow to Syria´s deadly unrest on a day the United Nations´ top peacekeeper said the conflict now bears the hallmarks of a civil war.

A shipment of attack helicopters is "on the way from Russia to Syria, which will escalate the conflict quite dramatically," Secretary of State Hillary Clinton said Tuesday, heightening pressure on Syrian President Bashar al-Assad´s staunchest international backer.

The accusation came as the U.N. said Syrian government forces had used helicopters in recent attacks on Syrians, corroborating for the first time similar activist reports.

The government shelled in several locations Tuesday, including districts of Homs and the town of Deir el-Zour in the east, activists said. In what appeared to be the most blistering attack, helicopter gunships and tanks bombarded the mostly Sunni town of Haffa for the eighth day, trapping residents inside as others scrambled to flee, fighters and activists said. The U.N. said its observers came under fire when attempting to visit Haffa and had to turn back.

Moscow has long resisted U.S.-led international attempts to force Mr. Assad to step aside. It has defended its weapons sales to Syria, saying Damascus is buying its weapons for defense only.

"We have confronted the Russians about stopping their continued arms shipments to Syria," Mrs. Clinton said. "They have from time to time said that we shouldn´t worry, everything they´re shipping is unrelated to their actions internally. That´s patently untrue."

A Kremlin spokesman couldn´t be reached to comment.

The U.S. comments came after a spokesman for Kofi Annan, the special envoy on Syria, said "diplomacy has intensified" on an international contact group meeting in which Russia and other influential states would be involved. "It´s coming together," Ahmad Fawzi told a press briefing in Geneva. Washington and Moscow have been in talks on a Syrian political transition.

But Syrian opposition members and residents alike have begun to describe the conflict in the language of civil war, with international observers comparing Syria to Lebanon in the 1970s, Yugoslavia in the 1990s and Iraq in the 2000s.

On Monday, U.S. and U.K. diplomats separately compared Syria with the Balkan conflict. Asked Tuesday by reporters from Reuters and Agence France-Presse whether he believed Syria´s conflict had become a civil war, U.N. chief peacekeeper Herve Ladsous responded: "Yes, I think we can say that."

Syrians who live in the country´s majority-Sunni heartland, meanwhile, say the conflict has taken on the dimensions of a sectarian conflict. On a recent day, Syrian refugees crowded a hospital in Tripoli, a northern Lebanese city less than 30 miles from Syria´s border. Overwhelmingly Sunni villagers and rebels from Syria, they said they recently fled killings, rapes and kidnappings. These people say they have been attacked by pro-regime forces at the urging of neighboring villagers from the same Alawite sect as President Assad, a narrative that melds with accounts of other massacres on majority Sunni villages in recent weeks.

"They want to wipe us off the map," said one man in the hospital, who identified himself as Ahmed, a 30-year-old Sunni Muslim farmer who runs a generator-repair shop in the village of Abu Houri, just a few miles over the border from Lebanon.

When Syrian government forces shelled his hamlet earlier this month, Ahmed said he ran outside in a vain attempt to save his cow. He lost an eye and sustained shrapnel wounds in his stomach and legs. He and several other wounded people from the area, including women and rebel fighters, were smuggled into Lebanon, several people in the hospital said.

It wasn´t possible to confirm the specifics of Ahmed´s account, but his analysis is now common in Syria´s Sunni heartland: He says that while the government mounted the attack on his village, he blames residents of a neighboring Alawite-dominated village for telling the military that his hamlet was harboring rebels.

"They think we´re going to attack them," he said.

Such village-against-village tensions in Syria´s countryside mark a shift in the 15-month-old uprising that began with peaceful protests, largely in cities, against President Assad´s regime. In a country at the crossroads of the Middle East´s major conflicts—with a complicated mix of Sunni majority along with Shiites, Christians, Alawites and other religious and ethnic minorities—Mr. Assad´s opponents took pains to avoid characterizing their struggle as sectarian.

But now, some antiregime activists openly charge the regime and its allies of "sectarian cleansing" of Sunnis. Some analysts now describe a pattern in which government attacks appear to be singling out Sunni strongholds among Alawite-populated villages or towns, particularly in the country´s northwest.

The Syrian regime insists it is battling foreign-backed terrorists and armed gangs.

Increasingly, Sunnis have described themselves as targets because their villages separate two Alawite communities or are situated on roads deemed as strategic by the Alawite population in the area and the regime.

The predominant theme is that Alawites, an esoteric Muslim sect associated with Shiism, are trying to gain ground. Extreme versions of the narrative offered by several activists and analysts hold that Alawites are attempting to clear neighboring areas of Sunnis, to consolidate a largely Alawite enclave near Syria´s coast with secure supply lines to Damascus.

Such a zone would reflect the separate coastal Alawite state created on and off between 1920 and 1936 when France was the colonial power in Syria, according to Osama Klaib, a Sunni lawyer from the Homs area and now a Tripoli-based member of the opposition Syrian National Council. The regime´s "last defense is to move to a coastal state," he said.

The alleged clearing of Sunni villages may also reflect that President Assad´s regime is losing control over the use of force in the conflict, said Fawaz Gerges, director of the Middle East Centre at the London School of Economics. The so-called shabiha—pro- government militias that the regime is said to have funded and armed over decades—appear to be acting ever more independently, he said. Their actions "might be the ultimate weapon that devours the regime itself and plunges Syria into all out sectarian strife," he said.

A Lebanese citizen by origin, Mr. Gerges said the violence in Syria now echoes the very beginnings of Lebanon´s 15-year civil war, which he witnessed. "You have massacres, assassinations, people beginning to flee the country, and the beginning of serious sectarian tensions. What the massacres really do is really intensify and escalate tensions, forcing neighbor to turn against neighbor," he said.

So far, there are no documented instances of large-scale reprisals against Alawites. However, opposition soldiers have recently spoken about responding in kind to kidnappings and killings conducted by what they say are soldiers and pro-regime thugs who are often from the Alawite minority.

One of Syria´s latest flash points is Haffa, a mountaintop village overlooking the coastal western city of Latakia. Haffa was never a focal point in the uprising, though it has been active in protests among other towns in a province seen as strictly loyal to the regime. A Sunni town ringed by Alawite villages, Haffa is just a few miles from President Assad´s family hometown, Qurdaha. It lies on the edge of the sweeping Alawite stronghold known as al-Sahel, Arabic for coast.

Syrian troops have been using the Alawite villages to launch artillery attacks on Haffa, according to the Syrian Observatory for Human Rights, a U.K.-based opposition watchdog. The group and other activists said more than 100 people were killed in major battles in Haffa, most of them government soldiers.

Similarly, residents of the countryside near Homs who spoke to a reporter in Tripoli recently said the villages of Al-Houz and Modan until recently were home to a mix of Alawites and Sunnis. But earlier this year, they said, Alawite residents moved out to an all-Alawite neighboring village called Qurniyah. Government forces then launched an offensive against the Sunnis that stayed behind, they said, saying that several people were killed.

This was done, they said, to assure that only Alawite loyalists remained along a road leading to the highway that connects Homs to the port city of Tartus to the west.

Among many Syrian Sunnis, the shift in mind-set over recent months has been dramatic.

In February, Ghassoub Halloum said sectarian killings and kidnappings in Tal Kalakh, a town outside of Homs, drove him, his wife and five young daughters out of Syria. At the time, he said he hoped that the scenario wouldn´t replicate itself across the country.

"We will not accept sectarianism, after all this," he warned at the time, echoing a broad sentiment among the opposition that being dragged into a sectarian war would feed into the Assad regime´s hands. "If civil war sparks, it will spread like wildfire,"

President Assad, and his father before him in their four-decade rule of Syria, have argued that their secular regime is a counterweight to the country´s fragile demographic makeup and a guarantor of stability.

Four months later, speaking from Tripoli where his family has sought refuge, Mr. Halloum said he now has a new and uncompromising view.

"I will be the first to strap on some explosives if it means I can kill even just three Alawites," he said. "They do not deserve to live." (Copyright © Dow Jones & Company, Inc.) 06/13/12)