U.S. Secretary of State Hillary Clinton said Tuesday that the U.S. is concerned about reports Russia is sending attack helicopters to Syria, as the U.N. peacekeeping chief said the Arab country is now in a full-scale civil war.

Secretary Clinton also said Russia's claims that its arms shipments to Syria are unrelated to the conflict are “patently untrue.” She said the U.S. has confronted Russia about stopping its continued arms transfers to the country wracked by 15 months of bloody unrest.

Her comments came as the U.N. peacekeeping chief, Herve Ladsous, told reporters that Syria has seen a “massive increase in the level of violence” and is now in an all-out civil war. He said the Syrian government has lost several areas to the opposition and wants to retake them using tanks, artillery and attack helicopters.

But U.N. spokesman Martin Nesirky backed away from that characterization, telling reporters later “it is not for the U.N. to designate in that way.” Nesirky, however, did confirm “a qualitative shift and intensification” of the violence in Syria.

Syrian rights groups say at least 34 people were killed Tuesday as government forces continued attacks on rebel strongholds and U.N. monitors reported an angry mob prevented them from reaching the embattled western town of al-Haffeh.

The Local Coordination Committees, an activist group with members throughout Syria, told VOA the casualties include 14 civilians dead in Deir al-Zour, 10 in Homs and eight in Aleppo. A number of government soldiers were among those killed.

LCC spokeswoman Rafif Jouejati said rebel fighters in al-Haffeh have been attempting to smuggle trapped civilians over the nearby Turkish border.

“We know there were some 30,000 residents trapped in the town of al-Haffeh and we also know members of the Free Syrian Army were trying to help residents flee the area and get transported to Turkey and that a small number of residents have been safely transported, but there are still thousands of residents trapped.”

Clashes in al-Haffeh began last week when security forces attempted to capture the strategic Sunni Muslim town. It is located close to the port city of Latakia and the Turkish border, and used by rebels as an active smuggling route for people and supplies.

The U.N. mission in Syria said a crowd of what appeared to be local residents in al-Haffeh surrounded U.N. observers and threw rocks and metal bars at their vehicles, firing guns at them as they left the area. None of the observers were injured.

Hundreds of rebels are facing a continued tank and helicopter-backed assault in al-Haffeh. The helicopter attacks – confirmed by the U.N. on Monday – are regarded as a significant escalation by government forces.

The United States has said it fears Syrian forces are planning to massacre civilians in the town.

LCC spokeswoman Jouejati told VOA that helicopter shelling and other aerial attacks by government forces have been occurring for months across Syria.

The spokesman for international envoy Kofi Annan said Tuesday that an international “contact group” will meet soon to discuss how to pressure Syria's government and opposition groups to implement the U.N.-Arab League envoy's tattered peace plan.

The contact group meeting has been in doubt because of Western opposition to Syrian ally Iran's involvement. The Iranian foreign ministry Tuesday welcomed a Russian proposal for Iran to be included despite strong reservations from the U.S., France and Britain.