"I personally believe I am being held as a hostage so that the Pakistanis can extort a larger compensation from the ship's insurers," Greek salvage master Nikos Pappas told AFP from Karachi through his lawyer in Athens.

The Tasman Spirit broke in two last August, leaking about 28,000 tonnes of crude oil into the sea off Pakistan, in the country's worst oil spill ever.

Pappas said his team from the Tsavliris company, called in after the accident, recovered more than 36,000 tonnes of oil from the tanker's hull which would have otherwise flowed into the sea. On Friday, the Pakistanis put him under house arrest together with the Tasman Spirit's crew of seven -- four Greeks and three Filipinos.

The row has dragged in the Greek foreign minister, George Papandreou, who has said he will contact his Pakistani counterpart to lodge a protest.

Pappas believes the move aims at putting pressure on the American Club, the ship's insurer, to pay its outstanding 10.5-million-dollar (8.9 million euro) debt to the Karachi Port Trust (KPT).

"Tsavliris already promised to pay its 480,000-dollar debt resulting from using the port's facilities and services during the operation. In return, Tsavliris demands I be released.

"The Pakistanis haven't responded yet. A port official said indirectly that if they release me, they have no guarantees the rest of their financial demands will be met."

On top of the KPT claim, Pakistan has said it will sue the Maltese-flagged tanker's Greek managers Polembros for one billion dollars in damages. Polembros blames the port's pilot for the accident in coastal waters.

The eight men expect to hear official charges in a hearing set for October 18. "Until now there are just rumours," Pappas said, asked to comment on reports they face charges of negligence that led to the oil spill.

All eight could be released from house arrest after paying an 8,620-dollar-per-head bond and depositing their travel documents with Pakistani officials.

"I am allowed to move within Pakistan, but in practice I can't even cross the street because I had to hand in all my travel documents," Pappas said.

The Hellenic Chamber of Shipping has spoken of a "blackmail ploy" by Pakistani authorities.

TERRA.WIRE