The authorities in the Pakistani city of Karachi have declared an emergency after the grounding of a tanker containing more than 67,000 tonnes of crude oil.
Coastal areas surrounding the city face an environmental disaster as it is feared the grounded vessel - the MV Tasman Spirit - may soon break up.
Heavy seas have been hampering salvage efforts
The Greek tanker, chartered by Pakistan's national shipping corporation, ran aground at low tide close to Karachi on 28 July.
The BBC's Zaffer Abbas, in Karachi, says oil gushing out of several cracks in the vessel has forced the authorities to abandon the salvage operation. The crew have been evacuated.
Senior officials admit they are not properly equipped to handle the crisis, but say some preventive measures are being taken to minimise damage to the harbour.
Fish lying dead
Our correspondent says the Pakistani navy has been put on alert to assist the authorities in the relief and rescue work.
Paramilitary troops have also been called out to cordon off one of the main beaches near an upmarket residential district, which has been almost completely covered by a thick layer of oil.
Eyewitnesses say hundreds of fish and turtles are lying dead on the beaches.
Officials say an aircraft with chemicals to stem pollution is being flown in from Singapore.
A British ship with fire-fighting equipment is being brought in as a precaution and is expected to reach Karachi soon.
An environmental adviser to the provincial government, Faisal Gabol, told the BBC the incident could turn into a major disaster.
He said all marine life in the area could be destroyed.