BEIRUT — Air strikes 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 UK-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 air strikes 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 militants.

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