US-backed fighters lay siege to Islamic State-held town

BEIRUT — U.S.-backed Syrian fighters have laid siege to the northern Syrian town of Tabqa, an Islamic State stronghold, two weeks after U.S. aircraft ferried forces behind militant lines to spearhead a major assault near the extremists’ de facto capital, Raqqa.

The Syrian Democratic Forces captured the Safsafeh area late Wednesday, completing the encirclement of the town, spokeswoman Cihan Sheikh Ehmed said Thursday. The Britain-based Syrian Observatory for Human Rights, which closely monitors the conflict, confirmed the account.

The March 22 airlift marked a deepening of U.S. involvement in Syria’s conflict ahead of a looming battle for Raqqa, the capital of the extremist group’s self-styled caliphate. SDF fighters captured an airfield outside Tabqa last week and have been trying to gain control of a major dam nearby.

Elsewhere in Syria, IS militants killed 33 young men in eastern Syria, close to the border with Iraq, according to Syrian opposition activists.