Activists on social media say car bomb is responsible for blast
An explosion at a base for Asian militants in northwestern Syria's Idlib city on Sunday killed at least 21 civilians, including eight children, a monitor said.
The strikes were the latest against militants and rebels in a week-old government offensive on Idlib, the last province in Syria to escape government control.
Rebel groups fighting in Syria count thousands of Asians among their ranks, including many from Central Asian states and members of the Muslim Uighur ethnic minority of China's Xinjiang Province.
"A large explosion on Sunday evening hit the base of the Ajnad al-Qawqaz faction in Idlib," said Syrian Observatory for Human Rights head Rami Abdel Rahman.
Eleven members of the same family, including eight children, were among those killed, Rahman said. Most of the non-civilian casualties were Ajnad al-Qawqaz fighters.
Government and Russian air strikes continued on Monday in several parts of Idlib, he said.
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He did not specify the cause of the blast, but activists on social media - who put the death toll higher - said a car bomb was responsible.
Ambulances and rescue teams rushed to the explosion site and efforts were underway to pull out the bodies and rescue injured trapped under the rubble of the targeted building and neighbouring houses, the monitor added.
The Syrian army and its allies launched an offensive in October to recapture the provinces of Idlib and Hama, and it has since been making swift advances.
Rebel base destroyed
Dozens of people were wounded, particularly fighters, according to Abdel Rahman, who said the base was "almost completely destroyed" and that nearby buildings were damaged.
The Ajnad al-Qawqaz group is battling alongside the Fateh al-Sham Front, a former al-Qaeda affiliate, to repel a Syrian government advance in the southeast of Idlib province.
The area has seen intense clashes prompted by a government offensive aimed at seizing a strategically vital highway between Damascus and second city Aleppo.
The Britain-based observatory, which relies on a network of activists across Syria, said government forces had seized more than 60 villages in the area since 25 December.
An alliance dominated by Fateh al-Sham controls much of Idlib province, where there are regular car bombings, often blamed on disputes between armed factions.
Some residents blame the Islamic State group for such attacks, although the group has no open presence in the province.