Dozens of Al-Nusra Front fighters killed following mosque bombing in north Syria

An explosion in a mosque in northern Syria killed 25 members of al-Qaeda's Syrian affiliate, including one of its leaders, as they attended Ramadan prayers, a monitoring group said on Friday.

Director of the Syrian Observatory for Human Rights (SOHR) Rami Abdel Rahman said the death toll could rise as dozens of civilians were also injured in the explosion during Iftar prayers in the city of Ariha.

"Twenty-five members of Al-Nusra Front, including a leader of the jihadist group, died in an explosion inside a mosque in the city of Ariha, in Idlib province," the Britain-based observatory said.

It was not immediately clear what caused the explosion.

Activist group the Syrian Revolution General Commission said "hundreds of civilians were assembled for an Iftar gathering with the Al-Nusra Front in the Salem mosque in the west of Ariha when the blast went off during evening prayers".

Civilians were also among those killed while worshipping during the holy Muslim festival of Ramadan, the group said, without giving further details.

Most of Idlib province is now under rebel control, after an alliance of opposition groups including Al-Nusra Front evicted government forces from their last strongholds.

11,189 killed since January

A report released by the Syrian Network for Human Rights (SNHR) on Thursday stated that at least 11,189 people, 1,547 of whom were children, have been killed in Syria since January 2015 by the Syrian government, Islamic State (IS) and other armed groups.

The report said that 1,358 people, including 413 armed fighters, were killed by IS.

At least 45 children and 102 civilians were killed by U.S.-led coalition airstrikes, while 10 children and 67 civilians were killed by the pro-Kurdish People’s Protection Units (YPG).

According to the report, other armed opposition groups killed 612 individuals, including 587 civilians, 136 children and 104 women.

At least 2,137 individuals were killed in June 2015 alone, the report added.

Over 350,000 have been killed since the beginning of the civil war, according to the report, much higher than the 230,000 figure cited by the SOHR.

The numbers were obtained by activists with access to various cities around the country.

Many places, however, were unreachable due to the Assad government preventing organizations from working on the ground.

Syria's civil war, which has left the country in ruins, was triggered by a bloody crackdown on peaceful protests in 2011 by the Assad government.

The conflict displaced half the population, with nearly four million Syrians seeking refuge in neighboring countries, with most of them going to Turkey, Lebanon, Jordan and Iraq.