Dozens killed as Islamist Syrian rebels reconcile with al-Qaeda
At least 16 people were killed as a missile struck a building in northwest Syria during a meeting between rebel groups.
"Eleven fighters from [Syrian al-Qaeda affiliate] al-Nusra Front and other Islamist groups were killed on Sunday, along with five civilians, when a ballistic missile hit a police station being used as a court in Salqin," in Idlib province, the Syrian Observatory for Human Rights [SOHR] said.
The UK-based monitoring group said it was unclear if the missile was fired by Russian or Syrian forces.
The monitor said the toll could rise further because a number of people had been seriously wounded in the strike.
The missile hit during a reconciliation meeting between members of the Nusra Front and the conservative Islamist militant group Ahrar al-Sham, who had exchanged fire in the town earlier the same day.
The two groups are leading members of the Army of Conquest alliance, a powerful coalition that took control of Idlib province last year.
The Nusra Front has been behind almost every major successful rebel push over the past two years of fighting - and few doubt that their determination is defending rebel villages from regime-allied militias.
Car bomb in Syria's Aleppo kills 23
Meanwhile, at least 23 people, most of them from the Ahrar al-Sham rebel group, were killed by a truck suicide bomber in Syria's Aleppo city on Monday.
SOHR said 19 fighters from the group and four civilians were killed in the blast in the Sukari district of the city.
The attack hit an Ahrar al-Sham checkpoint at the entrance to a security complex belonging to the group.
The Observatory said several prisoners being held by Ahrar al-Sham at a facility in the complex were also believed to have been killed, but it had no immediate toll.
The blast destroyed three buildings, and people were still missing under the rubble, the monitor added.
It was unclear who was responsible for the blast, but Ahrar al-Sham has been targeted by assassinations in the past.
In September 2014, most of its top leadership was wiped out in a devastating explosion at its headquarters in Idlib province that killed nearly 50 people.
More recently, the group has seen several of its commanders among a string of Islamist rebels killed in mysterious targeted killings.
The attacks have not been claimed, and suspicion has fallen on either the regime or the Islamic State group, which considers all forces that have not pledged allegiance to it to be rivals.
More than 260,000 people have been killed in Syria's war which began with anti-government protests in March 2011.