BEIRUT — Kurdish fighters were closing in on a northeastern Syrian town that is a key stronghold of the Islamic State group on Friday, activists said. The town and the surrounding province have become the latest battleground in the fight against the ISIS extremists who this week captured up to 220 Christians there.

The push on the eastern and southeastern edges of the town of Tel Hamees in Hassakeh province came after the Kurdish troops took dozens of nearby villages from the Islamic State extremists.

The British-based Syrian Observatory for Human Rights, which relies on a network of activists inside Syria, said the Kurdish fighters were supported by Arab militias and air strikes from the U.S.-backed coalition in their advance on Tel Hamees.

The Kurdish fighters, known as the People's Protection Units or YPG, have been making territorial gains since capturing the Syrian border town of Kobani from the Islamic State group last month following a several-month struggle.

But elsewhere in the same province — along the fluid and fast shifting front line — IS fighters captured dozens of mostly Christian villages in Hassakeh to the west of Tel Hamees — taking at least 220 Assyrian Christians hostage, according to activists.

Hassakeh province, which borders Turkey and Iraq, is predominantly Kurdish but also has populations of Arabs and predominantly Christian Assyrians and Armenians.

Nawaf Khalil, a YPG spokesman, said Kurdish forces have actually entered Tel Hamees and "totally liberated" the town from IS control, a claim that could not be immediately confirmed by The Associated Press.

The Observatory said ground battles and air strikes around Tel Hamees have killed at least 175 IS fighters in the past several days.

The Islamic State group still controls about a third of Iraq and Syria — much of it captured in a lighting blitz last spring and summer, as Iraqi army forces melted away in the face of the militant onslaught. On Thursday, video emerged of IS militants destroying ancient Mesopotamian artifacts in a museum in Mosul, Iraq's second largest city.

Elsewhere in Syria, at least eight civilians were killed in a car bomb that exploded outside the Bilal Mosque in the rebel-held town of Dumeir, east of Damascus. Many others were wounded in the blast, which occurred as worshippers were leaving the mosque following Friday prayers.

Another car bomb went off outside a mosque in Nasseriya, near Dumeir, also causing multiple casualties. It was not immediately clear who was behind the bombings.