The Islamic State jihadist group has executed 2001 civilians as well as 420 of its own members in Syria since declaring its caliphate 18 months ago, a monitoring group said Tuesday.
Among the dead civilians were some 930 members of the Shuaitat tribe who rose up against the jihadist organization last year after it captured their homeland in eastern Syria, the Syrian Observatory for Human Rights said.
The jihadist group has executed 420 of its own members, mainly foreign fighters, on charges of spying for foreign countries or because they were trying to escape and return home, the Britain-based monitoring group said.
Victims of Islamic State's executions in Syria also included over 1,000 government troops and loyalist militiamen as well as 253 rebel fighters and rival jihadists, the Observatory said.
On June 29, 2014, weeks after capturing swathes of neighbouring Iraq in a lightning offensive, the organization declared its leader Abu Bakr al-Baghdadi caliph and said he was entitled to the allegiance of all Muslims worldwide.
The group has deliberately cultivated a reputation for brutality with graphic videos showing executions of its prisoners, in an apparent effort to gain media attention and deter any opposition to its rule.
Islamic State has its origins in the Iraqi branch of al-Qaeda, but it split with the older jihadist organization when Islamic State sought to subsume its Syrian front organization, the al-Nusra Front, in 2013.
Al-Nusra's leader, Abu Mohammed al-Jaulani, resisted the move and his organization continues to fight alongside other rebels against the government of Syrian President Bashar al-Assad.
Islamic State, by contrast, is fighting for territory against Syrian rebels as well as Kurdish and government forces in both Iraq and Syria.
The United States has formed an international coalition targeting the group with air strikes as well as measures aimed at cutting its financial and arms supplies.
In the southern province of Daraa, Syrian government forces announced Tuesday that they seized a military base controlled by rebels, the Observatory and state media said.
State news agency SANA said government troops were also engaged in fierce clashes with rebels inside the neighbouring town of Sheikh Maskin in Daraa province.
Observatory director Rami Abdel-Rahman said the town is located on a strategic crossroads linking Damascus, the southern city of Daraa and the regime stronghold of Suweida to the east.
Rebels captured the town in November 2014 but were unable to capitalize on the gain when they failed to cut regime supply lines to Daraa city.
Daraa province, adjoining the Jordanian border, is a stronghold of more moderate rebel forces, although the al-Nusra Front was active in Sheikh Maskin.