Syrian fighter jets fired at least two rockets at the Palestinian Yarmouk camp in Damascus on Sunday, for the first time since the revolt against President Bashar Assad erupted last year, activists in the capital said.

They said dozens of people were killed when at least one rocket hit a mosque in the camp sheltering refugees who fled the violence in nearby suburbs of Damascus.

Yarmouk, in southern Damascus, is part of an arc sweeping from the east to southwest of the Syrian capital where Assad's forces have been trying for several weeks to push back rebels from the gates of his power base.

Meanwhile, rebels said they seized a Syrian army infantry training school near the northern city of Aleppo after five days of fighting with forces loyal to Assad.

A commander from the Islamist Tawheed Brigade said his men helped take the building on Saturday.

"At least 100 soldiers have been taken prisoners and 150 decided to join us. The soldiers were all hungry because of the siege," he added.