Greece says a seized ship carrying an "atomic bomb"-sized quantity of dynamite was destined for a phantom company in Sudan and the crew had been charged with transporting explosives.
Greek Shipping Minister Mr George Anomeritis said the ship, seized on Sunday by Greek special forces, did not report its cargo of explosives when coastguards stopped it after its movement aroused suspicion.
Police said the ship was carrying ammonia dynamite, an explosive used in mining, as well as 8,000 detonators and fuses.
The ship's papers said the cargo was for a firm identified as Integrated Chemicals and Development but contacts so far with Sudan indicated there was no such company, Mr Anomeritis said.
Tunisia - where the 680-tonne cargo of explosives was loaded on May 12th and 13th - and Sudan said there was nothing sinister about the shipment.
In Khartoum, Sudanese Foreign Minister Mr Mustafa Osman Ismail said it had summoned the Greek ambassador to Sudan to complain about the Greek action.
He told Sudan's official news agency the ship was "carrying materials for known civilian uses, ammonium nitrates".
Tunisian authorities said they had begun legal action against the Baltic Sky's owners for threatening to confiscate the cargo and resell it.
NATO, whose forces have boarded ships in the Mediterranean over the last few months as part of the US-led war on terror, said it had tipped off Greece about the Baltic Sky.