Four Greek and three Filipino crew members of the MV Tasman Spirit, which leaked 28,000 tonnes of crude oil into Pakistani coastal waters off Karachi on August 14, are barred from leaving Pakistan, as well as the Greek national heading salvage operations.

Foreign Minister George Papandreou contacted his Pakistani counterpart Khurshid Mahmud Kasuri to demand the immediate release of the Greek crew, the foreign ministry said Wednesday.

"The Pakistani FM said the oil spill caused a huge problem in Pakistan and that the men are held according to Pakistani law," a high-ranking Greek diplomat told AFP.

Pakistani authorities have said they will claim one billion dollarsmillion euros) in damages from the tanker's Greek managers, Polembros.

The oil spill occurred in a rich tropical marine ecosystem area, home to extensive mangrove forests, Green and Olive Ridley sea turtles, dolphins, porpoises, beaked whales and several species of lizards and sea snakes.

But the Greeks blame the Karachi port's pilot for the accident.

Stepping up pressure on Pakistan, Polembros said Wednesday it was considering asking British courts to seize Pakistani assets abroad as a countermeasure.

According to the company's spokesman David Gare, Polembros is eyeing foreign assets of the Pakistan National Shipping Corporation (PNSC), the firm that chartered the Tasman Spirit.

"We have English jurisdiction," Gare told AFP, asked where the likely recourse would take place.

A court hearing into the crew's case has been set for October 18. According to media reports, the crew face criminal charges for negligence in navigation and endangering lives.

The Hellenic Chamber of Shipping has criticized handling of the issue as a "blackmail ploy" by Pakistani authorities.

TERRA.WIRE