A Pakistan passenger train packed with holiday travellers went careering off the rails overnight, killing around 40 people and leaving more than 100 injured, police and railways officials said on Wednesday.
Pakistan has a history of rail disasters and it was not immediately thought that the country's militant insurgency had any role in the crash, but witnesses described a scene of horror and the death toll was believed likely to rise.
Hours after the accident, which occurred in a forested area near the town of Naushero Feroz in the southern province of Sindh, victims were said to be still trapped in at least three of the 15 coaches that hurtled off the track.
"It's a very painful scene," local officer Ghulam Qadir told AFP by phone. "People are trapped in the wreckage and there are cries for help. Policemen pulling out the dead and injured are drenched in blood."
The Karachi Express was en route to Lahore, filled with hundreds of people getting ready to celebrate the Muslim holiday of Eid al-Adha, when it went off the rails and ploughed into the ground.
"It was deep in the night and there was a huge crash," passenger Mohammad Afzal said by telephone.
Officials said doctors and aid workers were struggling to cope with the large numbers of casualties. Local people came by the hundreds to help, carrying the injured away on rickshas, motor-scooters and donkey carts.
Police said rescuers were fighting darkness and bitter cold, and did not have sophisticated tools to cut open the carriages or sufficient torches to help them work.
Local police officer Yasin Bodio, giving a preliminary toll, said that around 40 people were killed and more than 100 were injured.
"The death toll could go higher," he said.
A senior Pakistan Railways official, Asad Saeed, said: "It appears to be an accident but we have ordered an investigation to ascertain the cause."
He said 15 of the train's 17 coaches had gone off the rails.
Hundreds of people have been killed in recent years on Pakistan's ageing railway system. Casualty figures are often high because carriages are packed with many more people than they are designed for.
Millions of people across Pakistan travel during the Eid al-Adha holiday.
Pakistan suffered its worst train disaster in more than a decade in 2005 when three trains ploughed into each other in Sindh province, killing around 150 people. More than 350 people were killed in a 1990 train smash. (AFP)