Airstrikes pounded the south of Syria¡¯s Idlib region on Thursday, a rebel official and residents said, despite a cease-fire that had halted a fierce army offensive against the rebel stronghold two weeks ago.

Government warplanes bombed the south Idlib countryside for the first time since, including Maarat al-Numan town, the Syrian Observatory for Human Rights, a U.K.-based monitor, said.

Mohammad Rashid, spokesman for the Jaish al-Nasr rebel faction, said the raids had intensified after strikes on a few positions in the rural west of Idlib in the past two days.

Idlib, in Syria¡¯s northwest corner, is the last big chunk of territory still in rebel hands after more than eight years of civil war.

Idlib enjoyed a lull in airstrikes after Damascus and its ally Moscow declared a cease-fire on Aug. 31 following five months of bombing which the United Nations says killed hundreds of people.

This was the second such truce announced there in a month. A cease-fire in early August collapsed within three days, after which the Russian-backed army of President Bashar Assad pressed its offensive and gained ground.

Turkey, which supports some rebel factions, brokered a ¡°de-escalation¡± deal with Russia in 2017 that sought to curb fighting in Idlib. It does not cover jihadi militants.

Rebels said on Wednesday that pro-government forces were massing on the front line.