Lahore: A speeding bus carrying over 100 passengers fell into a ravine killing at least 27 people and injuring 69 others in Pakistan's Punjab province, police said today.

The overloaded bus was going from Kohat to Raiwind when the accident took place in Kallar Kahar town last night.

"The passengers were going to Raiwind to attend an annual religious congregation," said Muhammad Afzal, the Station House Officer of Saddar Police Station.

The death toll in the accident has risen to 27, with three more injured persons succumbing to their wounds during treatment, Dunya News reported.

The cause of the accident was not known but apparently overloading was the reason as it was carrying around 100 passengers, the police said.

Thirteen of the injured were rushed to Rawalpindi because of their serious condition while many injured were shifted to nearby hospitals, the Dawn News reported.

The bus originally was to go to Raiwind via Islamabad- Lahore Motorway but it opted for another route. "The motorway is closed after 10 pm due to smog and overloaded buses are fined on the motorway because of which the driver opted to go through Grand Trunk Road," Afzal said.

"The driver was unfamiliar with this area and he was driving the bus at high speed. The bus fell into the ravine while it was passing through a slope," he said.

Punjab Chief Minister Shehbaz Sharif expressed grief over the loss of lives and sought a report of the accident.

He also ordered the authorities to provide immediate medical treatment and relief to all those injured in the accident.

Road accidents are common in Pakistan. Most of them are caused by careless driving, bad roads and faulty vehicles.

In April 2014, some 15 people were killed in a bus crash in Kallar Kahar, the same area where last night's accident had occurred.