Dozens of fighters have been killed in clashes between two jihadist factions in northern Syria, reports said.
The battles involved Tahrir al-Sham, formerly an al-Qaeda affiliate, and Jund al-Aqsa, regarded as close to so-called Islamic State (ISIS).
UK-based Syrian Observatory for Human Rights (SOHR) said the fighting was a war for influence in Idlib province.
Inter-factional fighting has beleaguered insurgents since early on in the Syria war.
Last month, a hardline Islamist group, Ahrar al-Sham, was also involved in days of clashes in Idlib with Jabhat Fateh al-Sham (JFS), which rebranded itself as Tahrir al-Sham, an alliance of jihadist groups, at the end of January.
Nearly 70 people have been killed in the latest fighting, which began on Monday morning, according to the SOHR and a rebel commander.
Tahrir al-Sham has captured six villages from Jund al-Aqsa, the SOHR said.
The two sides are also reported to have clashed in the north of neighbouring Hama province.
Idlib province, in the country’s north-west, has long been a rebel stronghold, dominated by Ahrar al-Sham and JFS/Tahrir al-Sham.
The SOHR said the fighting erupted after Jund al-Aqsa carried out a suicide bombing on Tahrir al-Sham, killing nine people, AFP news agency reported.
However, a Jund al-Aqsa commander told the Associated Press that Tahrir al-Sham had attacked his group’s positions first.
The two factions were allied for a short time last year but fell out soon after.