ISLAMABAD - At least two people were killed and over 100 others injured when two passenger trains collided near Karachi in southern Pakistan early Monday morning, reported local media.

The accident took place at about 4:00 am local time when a passenger train hit another from behind in Bin Qaisim town, some 50 km southwest of Karachi.

One Lahore-to-Karachi train, Millat Express, pulled up on the track due to some technical failure when another Karachi-bound train from Lahore, Shalimar Express, rammed it from the rear at a speed of 70 to 80 km per hour, said railway officials.

"I heard a big bang in sleep when two trains collided," a passenger was quoted as saying.

Desperate cries for help were heard everywhere in the complete dark compartments after the accident happened, said the passenger.

Both trains derailed following the collision, local media quoted railway officials as saying.

According to railway officials, both the front part of Shalimar and the rear part of Millat were seriously damaged and a driver on Shalimar and a conductor on Millat were killed in the collision.

Ambulances and rescue teams were dispatched from Karachi to the site after the accident was reported.

All the injured people have been admitted to the Jinnah Hospital in Karachi, said rescuers, adding that some of the passengers were still trapped inside the badly damaged compartments and they were trying to cut open the compartments to get them out.

Initial investigation showed that the failure of the signal system had caused the accident.