BEIRUT Syrian rebels used captured tanks to launch a fresh offensive on a government complex housing a police academy near Aleppo and clashed with government troops protecting the strategic installation on Sunday.
The military responded with airstrikes to defend the complex, which also includes several smaller army outposts in charge of protecting the police academy.
Rebels have logged a string of strategic victories over the past few weeks, especially in the northeast where Aleppo is located.
Capturing the complex near Aleppo would be another blow to the regime that has in recent weeks lost control key infrastructure in the northeast including a hydroelectric dam, a major oil field and two army bases along the road linking Aleppo with the airport to its east.
Rebels have also been attacking deeper into the heart of Damascus, posing a stiff challenge to President Bashar Assad regime in its seat of power.
Rami Abdul-Rahman, the director of the Britain-based Syrian Observatory for Human Rights, said rebels have been trying for months to storm the complex west of Aleppo in the suburb of Khan al-Asal.
Rebels have also been trying for weeks to capture Aleppo's International Airport.
There were no reports of fighting for the facility on Sunday. But there have been battles around a section of the highway the army has been using to transport troops and supplies to a military base within the airport complex.
Assad's forces have been locked in a stalemate with rebels in Aleppo since July, when the city became a major front in the civil war.
Months of heavy street fighting have left whole neighborhoods in the city in ruins, carving it up into areas controlled by the regime and others held by rebels with both sides shelling each other's positions.
On Friday, regime forces fired three missiles into a rebel-held area in eastern Aleppo, hitting several buildings and killing 37 people, according to the Observatory. It said the strike apparently involved ground-to-ground missiles.
A similar attack on Tuesday in another impoverished Aleppo neighborhood killed at least 33 people, almost half of them children.
A senior Syrian opposition leader said Sunday that his umbrella group has suspended participation in meetings with its Western backers and their Arab allies because of their indifference over the regime's attacks on the Syrian people in Aleppo and in other cities.
"Assad has reached the stage of real genocide amid Arab silence and we renounce that," said George Sabra, vice president of the Syrian National Coalition. He spoke to reporters in Cairo after meeting the Arab League chief Nabil Elaraby.
The United Nations says at least 70,000 people have been killed since Syria's uprising against Assad's authoritarian rule began nearly two years ago.
On Friday, a statement posted on the Facebook page of Sabra's opposition group said its leaders would not travel to Washington or Moscow for any talks to protest the international community's "silence over crimes committed by the regime."
The statement also said that the opposition leaders would boycott a meeting next month in Rome of the Friends of Syria, which includes the United States and its European allies.
In Washington, the State Department condemned rocket attacks on Aleppo, saying in a statement late Saturday the strikes are the "latest demonstrations of the Syrian regime's ruthlessness and its lack of compassion for the Syrian people it claims to represent."
Efforts to stop the bloodshed in Syria so far have failed, leaving the international community at a loss of how to end the civil war.