BEIRUT (Reuters) - Clashes between rival insurgent groups broke out in Syria’s Idlib region in some of the heaviest fighting between Islamist factions which hold sway in the northwestern province, war monitors reported on Wednesday.

The Syrian Observatory for Human Rights said Hayat Tahrir al-Sham - a jihadist alliance that includes al Qaeda’s former Syria branch - had attacked positions of Ahrar al-Sham, a more moderate rival Islamist group allied with mainstream rebel factions.

The clashes began late on Tuesday, the British-based Observatory said and an online statement from Ahrar al-Sham blamed Tahrir al-Sham for starting the violence.

The two sides clashed earlier this year in a long-standing fight for influence in Idlib, where insurgents maintain a stronghold even as much of the rest of western Syria has been recaptured by government forces and their allies.

Fighting had on Wednesday spread to areas across Idlib, including the town of Saraqeb in the east, Dana and Sarmada in the northeast and Bab al-Hawa near the Turkish border, the Observatory reported.

Several fighters and at least two civilians had been killed, it said.

Idlib province is dominated mainly by Islamist groups although the moderate Western-vetted Free Syrian Army (FSA) groups have a presence there.

The province, which borders Turkey, has long witnessed infighting between the main jihadist groups vying for power.

Although opposed to Syrian President Bashar al-Assad’s rule, insurgents are riven by deep divisions on ideology and rivalry that erupts occasionally in deadly clashes. Rebels including Ahrar al-Sham say it takes the focus away from the fight against Damascus and weakens insurgents.

Ahrar al-Sham has sided with FSA groups in the fight with Tahrir al-Sham which was formed in January from a merger of several Islamist factions and Syria’s former al Qaeda affiliate, known as the Nusra Front until it cut ties with al Qaeda last year.