More than 55,000 people were killed in the Syrian civil war in 2015, including more than 2,500 children, the British-based Syrian Observatory for Human Rights said Thursday.

The group said it tallied 55,219 deaths during 2015, the fifth year of the war. The total number of deaths since the conflict began in March 2011 has now surpassed 260,000, although the number killed in 2015 was less than the 76,021 killed in 2014. The war has displaced more than half the country's pre-war population and caused more than 4 million to seek refuge in other countries, reported The Telegraph.

Among the 55,219 people killed in 2015 were 13,249 civilians and 2,574 children, the group said.

The majority killed were Islamic extremists fighting to overthrow Syrian President Bashar al-Assad, including more than 16,000 jihadists from the Islamic State group, al-Nusra Front and similar organizations, and nearly 8,000 anti-government rebels, according to AFP.

The observatory said that more than 17,686 people from the Assad regime were also killed, more than 8,800 of them army troops, more than 7,000 pro-regime militia and 378 of Lebanon's Hezbollah.

A total of 1,214 fighters from foreign countries died fighting for the Assad regime, including from Iraq, Iran and Afghanistan.

An additional 274 people died but their identifies could not be established, the observatory said.

In all, more than 95,000 regime forces, 45,000 rebels and 40,121 jihadists have been killed during the war.

On Thursday, the Islamic State group claimed responsibility for the Wednesday bombing of two restaurants in a Kurdish city in northeastern Syria, which killed at least 16 people and injured more than 30, according to The Associated Press.