At least 12 Pakistani workers have been killed and more than 50 injured after a huge blast ripped through an oil tanker at a ship-breaking yard, trapping others inside the vessel.
The leader of a ship-breaking workers union said fire had engulfed the vessel moored in Gadani, 45km northwest of the port city of Karachi.
"Things are really bad here," union president Basheer Mehmoodani told Reuters. "There's an unclear number of workers said to be trapped in the burning ship."
At least 12 people were killed and another 58 injured in the blast, said Zulfiqar Bokhari, a senior administrative official in the area.
Nasir Mansoor, a representative of the National Trade Union Federation of Pakistan, said the explosion sent pieces of metal flying up to two kilometres away.
The blast occurred in the fuel tank of the ship, which was still on fire, he said.
Firefighters from Karachi and from the air force and navy were attempting to put out the blaze, he said.
Mansoor said the firefighters would have to wait for the fire to die out "as they lack the foam required douse it."
Labourers in Gadani often work in poor conditions without basic protective gear.
The Gadani ship-breaking industry has fallen on hard times recently and employs about 9,000 workers, fewer than in its boom years at the end of the last decade.