(CNN) A car bomb in the Syrian city of Idlib has killed nine fighters from a former al Qaeda affiliate, hours after the group took control of the city and most of the region, the Syrian Observatory for Human Rights reported on Twitter.
Two other people were killed and dozens injured by the booby trapped vehicle that hit a gathering of members of Hayat Tahrir Al-Sham (HTS), a coalition of Salafi jihadist groups that include Fateh al-Sham, which was previously known as Jabhat al Nusra before renouncing its ties to al Qaeda.
HTS took over most of Idlib province at the weekend after pushing out Ahrar al-Sham, another Islamist group supported by Turkey and a number of Gulf countries, SOHR reported.
Following agreements signed on Friday and Sunday 21, fighting between the two groups decreased but didn't stop, according to SOHR.
Sourcing accurate and reliable information out of Syria is very difficult. SOHR, which is a small group run from the UK with activists on the ground, is seen as one of the most reliable sources.
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SOHR said Idlib was "witnessing a state of alert" as Ahrar al-Sham withdrew from the city to the countryside.
HTS and Ahrar al-Sham were once allies and fought alongside each other to capture most of Idlib province from the Syrian government in 2015.
Idlib is one of the last Syrian provinces still beyond regime control.
Last week a senior US general confirmed that the US has ended a classified CIA program to arm rebels in Syria fighting President Bashar al Assad.