At least 40 people have been killed and more than 120 injured after the Sir Syed Express train collided with the Millat Express, which had derailed and slid onto the adjoining track, in Pakistan before dawn on Monday.

The collision took place near the town of Dharki, about 440km (273 miles) north of Pakistan’s largest city of Karachi.

Rescuers and villagers have been working throughout the day to pull survivors and the dead out of the crumpled train cars.

Cries for help pierced the pre-dawn as passengers climbed out of overturned or crushed rail cars.

Heavy machinery arrived later in the day to cut open some cars in the hopes of rescuing several people still believed to be trapped.

The military deployed troops and helicopters to assist.

“The challenge for us is to quickly rescue those passengers who are still trapped in the wreckage,” said Umar Tufail, a police chief in the district.