TEHRAN (Press Shia) – Infighting between two major terrorist groups in Syria's militant-held Idlib province has killed at least 14 people in the past 24 hours, a monitor said Wednesday.

The fighting involves Hayat Tahrir al-Sham (HTS), led by a former Al-Qaeda affiliate, against one-time ally Ahrar al-Sham, a powerful terror group.

The so-called Syrian Observatory for Human Rights said the Takfiri militants from the two sides were engaged in clashes across the province in northwest Syria that killed 11 rebels and three civilians in the last 24 hours.

"These are the most violent and widespread clashes that have taken place between Ahrar al-Sham and Tahrir al-Sham," Observatory director Rami Abdel Rahman told AFP.

"The clashes are ongoing across all of the province, with territory changing hands… It's an existential battle," he added.

An AFP correspondent in the province also reported fighting in several areas, particularly in the town of Sarmada and around the towns of Saraqeb and Al-Dana.

He said both sides had set up multiple checkpoints inside and around provincial capital Idlib city.

Idlib city was only the second provincial capital to fall from government control, and the province is one of the last remaining strongholds of the rebels.

Syria has been gripped by civil war since March 2011 with various terrorist groups, including Daesh (also known as ISIS or ISIL), currently controlling parts of it.

According to a report by the Syrian Center for Policy Research, the conflict has claimed the lives of over 470,000 people, injured 1.9 million others, and displaced nearly half of the country’s pre-war population of about 23 million within or beyond its borders.