(CNN) -- After eight days of bombardment, Syrian government forces reclaimed the northwestern town of al Haffa on Wednesday, forcing rebels to stage a dawn retreat.
President Bashar al-Assad's government said through the state-run Syrian Arab News Agency that its forces had "restored security and calm after clearing it from the armed terrorist groups."
It said it had seized a cache of armaments, including sniper rifles, rocket-propelled grenades and explosive devices.
An opposition group said rebel forces had withdrawn from Haffa and surrounding villages "in order to preserve the lives of civilians." The London-based Syrian Observatory for Human Rights said Haffa had been under heavy shelling for eight consecutive days.
Fighting raged elsewhere as well, as the Syrian military pummeled cities from both the ground and sky, opposition activists said.
The Homs province city of Rastan came under fresh attack from planes and rocket-propelled grenades, the opposition Local Coordination Committees of Syria said.
At least 77 people were killed Wednesday, including 23 in Homs province, the group said.
CNN cannot independently confirm reports of casualties because the Syrian government has restricted access by international journalists.
Escalating violence has prompted the United Nations peacekeeping chief to become the first official from the global body to declare the Syrian crisis a civil war.
"Yes, I think we can say that," Herve Ladsous said Tuesday. "Clearly what is happening is that the government of Syria lost some large chunks of territory, several cities to the opposition, and wants to retake control."
But U.N. Spokesman Martin Nesirky told reporters Wednesday that it is up to the International Committee of the Red Cross in Geneva to determine when the crisis in Syria is considered a civil war.
Asked about Ladsous' characterization of the fighting, Nesirky said, "I think it's clear that it's not for us to determine or formally characterize the nature of the conflict in Syria," he said. "Everyone has been speaking about the escalation of violence, use of tactics and use of weaponry. That is where the focus is: to stop that." The United States and Russia, meanwhile, accused each other of arming sides in the conflict.
Washington said Russia was sending attack helicopters to Syria, which U.S. Secretary of State Hillary Clinton feared would "escalate the conflict quite dramatically."
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."
But the Russian state-controlled arms trader Rosoboronexport said it will fulfill its arms contract with Syria, the state-owned RIA Novosti news agency reported.
Russian Foreign Minister Sergey Lavrov dismissed U.S. claims.
"We are completing right now the implementation of contracts that were signed and paid for a long time ago," he said after talks with his counterpart in Iran. "All these contracts concern exclusively anti-aircraft defense.
"We are not delivering to Syria, or anywhere else, items that could be used against peaceful demonstrators," he said. "In this we differ from the United States, which regularly delivers riot control equipment to the region. But for some reason the Americans consider this to be fine."
Lavrov said it was the United States that was escalating the conflict by arming the Syrian opposition.
But Nuland told reporters that that was not the case. "The United States is sending no military equipment to the Syrian opposition," she said Wednesday. "What we are doing is providing nonlethal supports ... primarily communications gear and we are also one of the largest donors of humanitarian relief for the Syrian people, medical supplies, etc., through the U.N. agencies, some $52 million so far."
U.N. observers had attempted to reach al Haffa but were prevented by government supporters who lay down on the road, the opposition Syrian Observatory for Human Rights said.
Angry crowds surrounded the observers' cars and hurled stones and metal rods at the vehicles, said Sausan Ghosheh, a spokeswoman for the U.N. monitoring mission in Syria.
As the monitors were leaving the area, an unknown source fired at three vehicles, she said.
The Syrian regime had a different story. State-run television said some residents in the province "tried to explain to members of the observers' mission their suffering from terrorist groups, but the observers did not listen to them. Instead, one of their cars hit three citizens," two of whom were in critical condition.
The peacekeeping chief's spokesman 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.
Thousands of Syrians have died in the violent uprising. Opposition groups estimate the death toll to range from at least 12,000 to more than 14,000.
Al-Assad's government lashed out at Washington, saying it "is continuing its blatant interference in the internal affairs of Syria, its open support for terrorists, covering up terrorists' crimes, distorting facts about Syria at the United Nations, and extorting countries and the international community to beleaguer Syria," the state news agency reported Wednesday.
At least 60 people were killed Tuesday, the Local Coordination Committees said. Among the victims was a family of six, including an infant. They were killed in Aleppo province when a shell landed on their home, the opposition group said.
The state-run new agency said 36 "martyrs from the army and law enforcement forces" were buried Tuesday.
CNN's Richard Roth, Pam Benson, Holly Yan, Phil Black and Salma Abdelaziz contributed to this report.