Militants shot down a helicopter on Saturday and briefly occupied a town, in an escalating turf war with Iraq’s government that has killed at least 25 people in two days, police said.

All four crew members were killed when their helicopter was downed during a reconnaissance flight over the town of Karma in Iraq’s western province of Anbar, where the army is engaged in a standoff with anti-government fighters.

Sunni Islamist insurgents have been gaining ground in Iraq over the past year and in recent weeks overran several towns, raising the stakes in a conflict against the Shi’ite-led government that made last year the deadliest since sectarian civil strife began to abate in 2008.