BEIRUT - Islamic State group militants have been driven out of Syria's Idlib province, two days after making an incursion into the region bordering Turkey, a war monitor said Monday.

IS fighters captured the Idlib village of Bashkun at the weekend after clashes with Hayat Tahrir al-Sham, an alliance of rebel forces dominated by a former Al-Qaeda affiliate.

"After fierce fighting, Tahrir al-Sham has once again chased IS out of Idlib," said the Syrian Observatory for Human Rights, a Britain-based monitor.

The setback comes more than three years after IS was first expelled from the province in northwestern Syria after battles with rival militants and rebel groups. IS has seen the so-called "caliphate" it declared in 2014 across parts of Syria and Iraq crumble in recent weeks, losing key cities such as Raqa and Mosul.

 Iraqi Prime Minister Haider al-Abadi on Saturday declared victory in the three-year war to expel the militant group which at its height held roughly one third of the country's territory.

It now holds just a few patches of territory in Syria.

More than 340,000 people have been killed in Syria's multi-faceted war since the conflict began with anti-government protests in March 2011.