Fighters with the Islamic State in Iraq and Syria have gained control of a major military base in Syria, according to multiple reports.
The extremist group ISIS now effectively controls all of Raqqa province, which borders Turkey and the province of Aleppo. The capital city of Raqqa has served as the group’s headquarters.
{mosads}Tabqa air base was the last stronghold for Syrian President Bashar Assad in the Raqqa province and marks the third military base militants have recently captured.
The moves could increase pressure on the Obama administration to launch airstrikes against ISIS in Syria. U.S. officials have said the administration is considering the strikes, which are already being carried out against the group in Iraq.
Syrian government forces launched airstrikes against ISIS, but the militants entered the grounds of the air base on Sunday. The group gained control after Syrian forces withdrew, according to The New York Times.
Syria’s state news service confirmed troops withdrew from the air base, but reported that the forces successfully “regrouped” and were fighting nearby, the Times noted.
Syrian Observatory for Human Rights, a U.K-based opposition group tracking the conflict, reported a “large number” of dead Syrian soldiers after clashes at the air base.
The organization said ISIS fighters were seen carrying the severed heads of soldiers who were killed during the battle. This report comes nearly a week after ISIS released a graphic video showing the beheading of U.S. journalist James Foley, who was captured in Syria in November 2012.