At least 43 people were killed and dozens injured Monday when a packed Pakistani inter-city train ploughed into another express that had derailed just minutes earlier, officials said.

Several people were trapped for hours in the mangled wreckage left by the collision near Daharki, in a remote part of rural Sindh province, before rescue workers with specialist equipment could reach them.

Huge crowds from nearby villages gathered around the carnage of the overturned Pakistan Railways carriages, with twisted and shredded metal scattered across the ground, along with piles of luggage.

On Monday evening, army and civil engineers led a mass effort to clear and repair the tracks, with one official saying they hoped the line would be open by midnight.

The double accident happened around 3.30am (2230 GMT) when most of the 1,200 passengers aboard the two trains would have been dozing.

"We tumbled upon each other, but that was not so fatal," Akhtar Rajput, a passenger on the train that derailed, told AFP.

"Then another train hit us from nowhere, and that hit us harder. When I regained my senses, I saw passengers lying around me, some were trying to get out of the coach.”

"I was disoriented and trying to figure out what happened to us when the other train hit,” Shahid, another passenger, told AFP.

The Millat Express was heading from Karachi to Lala Musa when it derailed, its carriages strewn over the tracks as the Sir Syed Express from Rawalpindi arrived minutes later in the opposite direction, smashing into it.

Most of the dead were pulled from the derailed train, officials said.

Umar Tufail, a senior Daharki police officer, said 43 people were killed and dozens injured.

A spokesman for Pakistan Railways put the toll at 33, but communications with the crash site were difficult because its remote location.

One rescue worker described having to stand on top of his vehicle to get a phone signal.

Local farmers and villagers were the first to join passengers in trying to pull survivors from the crumpled carriages, reaching into broken windows and roof hatches.

A clip aired on a local channel showed medics giving an intravenous drip to a conscious passenger whose lower torso was trapped between crushed carriage benches.

The dead were laid out in rows on train seat benches and covered in traditional scarves.

Communication problems 

The accident happened on a raised section of track surrounded by lush farmlands.

Interior Minister Sheikh Rashid, a former railways minister, said the track where the accident occurred was built in the 1880s and described it as "a shambles”.

Current minister Azam Swati described the section of railway as "really dangerous”, but said authorities had been waiting to upgrade the network with funding from the multibillion dollar China-Pakistan Economic Corridor project.

"In case there is a delay [with funding], we will rebuild this track with our own money,” he said.

The Pakistan army and paramilitary rangers from nearby bases were at the site to help.

Prime Minister Imran Khan said he was "shocked” by the accident and promised a full inquiry.

Gul Mohammad, who works with the Edhi Foundation ambulance service, said communication problems were hindering the coordination of the rescue efforts.

"I am talking to you as I stand on the rooftop of my ambulance for better signal,” he told AFP.

Train accidents are common in Pakistan, where the network has seen decades of decline due to corruption, mismanagement and lack of investment.

The majority of train passengers in Pakistan are working-class people who cannot afford the quicker bus journeys.

More than 300 people were killed and 700 injured in 1990 when an overloaded 16-carriage inter-city train crashed into a stationary freight train near the city of Sukkur in Sindh.

More recently, at least 75 people died when a train caught fire while travelling from Karachi to Rawalpindi in October 2019.

The rest of the transport sector does not fare much better, with two major passenger plane crashes in the past five years and thousands of road accidents.