BEIRUT (AP) -- At least 10 people were killed Friday when airstrikes hit several rebel-held neighborhoods in Syria's contested northern city of Aleppo and neighboring Idlib province, anti-government activists said.

Aleppo, Syria's largest city and former commercial center, has seen sporadic clashes since the February 27 cease-fire, as government troops advanced, boxing in opposition-held areas from all sides except for a corridor from the northwestern edge of the town.

The Britain-based Syrian Observatory for Human Rights said at least 10 people were killed in the airstrikes in Aleppo's Bustan al-Qasr neighborhood and other parts of the city controlled by rebels.  The Observatory described the series of airstrikes as the most intense on the city since the cease-fire began.

Two activist-operated media outlets, the Syrian Revolution Network and Azaz Media Center, said at least seven people were killed. The discrepancy couldn't immediately be reconciled, but divergent death tolls are common soon after attacks.

In the northern Idlib province, the Local Coordination Committees and Saraqib Today, both anti-government media platforms, said at least three people were killed in an airstrike on a village east of Saraqib.

The February cease-fire has been teetering amid rising violence. U.N.-brokered talks in Geneva to resolve the Syria conflict have been bogged down after the Western-backed opposition delegation suspended its participation and the warring sides traded accusations.