At least 22 people were killed and more than 40 injured when two passenger trains collided on Thursday morning near Karachi's Landi Railway Station, officials said.

Witnesses described watching in horror as Zakaria Express from Multan rammed into Fareed Express from Lahore, which was parked there, with the roar of the crash swiftly followed by the screams of people trapped inside.

At least two carriages from the trains overturned due to the collision. TV footage showed the trains had suffered heavy damage. The train operation came to a complete halt after the accident.

Officials said rescuers armed with metal-cutting equipment and heavy cranes had managed to pull all the passengers from the twisted wreckage.