At least 18 people, including women and children, were killed and 39 injured when a passenger bus plunged into a ravine in Pakistan's eastern Punjab province early on Saturday.

The bus, heading to Rawalpindi from Lahore, the capital of Punjab province, fell down in the ravine near Jhelum, 100 km southeast of Islamabad, state-run PTV reported.

Four of the injured were stated to be in critical condition.

Witnesses said the bus skidded off the road while taking a turn.