Ladsous spokesman Dwyer called the firing on peacekeepers' vehicles "deliberate and direct," and said U.N. officials were evaluating whether the 300 unarmed peacekeepers in Syria are safe enough to continue their activities. "We're looking at all situations," he said.
U.S. Secretary of State Hillary Clinton expressed concern Tuesday about reports that Russia may be sending attack helicopters to Syria. Speakinng at an event in Washington, Clinton said the United States has confronted Russia about stopping its arms shipments to al-Assad's regime.
State Department spokeswoman Victoria Nuland said the United States has been "pushing the Russians for months to break their military ties with the Syrian regime and they haven't done it. And instead they keep reassuring all of us that what they are sending militarily to Syria can't be used against civilians. And now what are we seeing? We are seeing the Syrian government using helicopters to fire on their own people from the air."
Deputy Secretary of State William Burns will talk with a Russian official to discuss Syria at an economic meeting Thursday in Kabul, the State Department said.
Clinton said that there appears to be no easy solution for ending the bloodshed in Syria. "We are approached on a regular basis by representatives of different groups within Syria who are terrified of what comes next," she told an audience at the Brookings Institution. "So, how we manage a political transition -- assuming we could manage a political transition -- how we provide reassurance and some level of protection to Christians, Druze, Alawites, Kurds, Sunni business leaders and the like; how we prevent a massive inflow of refugees across the Jordanian and Turkish borders; how we protect Lebanon from getting caught up in the sectarian divides that afflict them as well as Syria. If these questions had self-apparent and actualizing answers, I would certainly share them with you."
Meanwhile, Syria said an "armed terrorist group" attacked the state-run al-Ikhbaria TV channel in al-Haffa in "an attempt to stop national media from conveying the truth."
The group opened fire on a car, and "al-Ikhbaria correspondent Mazen Mohammad was hit in his hand while cameraman Fadi Yakoub was hit in his chest," state-run news agency SANA reported.
SANA reported that 36 "martyrs from the army and law enforcement forces" were buried Tuesday.
The latest reports of violence came a day after government forces fired indiscriminately from helicopters on a town on the outskirts of Jabal Al-Zawiya, inflicting scores of casualties among civilians and rebel forces, an activist told CNN.
Ibrahim Swed, speaking from the Idlib province town, said fighting between the Free Syrian Army and government forces persisted for six hours and resulted in 32 deaths.
Al-Assad defined by indecision, violence
The United Nations estimates that more than 10,000 people, mostly civilians, have died since the crisis erupted in March 2011. Opposition groups give estimates ranging from at least 12,000 to more than 14,000.
CNN cannot independently confirm reports of casualties or violence in Syria, as the government has restricted access by international journalists.