MOSCOW, (Reuters) – The hijackers of a cargo ship  that disappeared off the coast of France threatened to blow it  up if their ransom demands were not met, Russian news agencies  said yesterday.

Russia on Tuesday arrested eight people on suspicion of  hijacking the Arctic Sea off the Swedish coast and sailing it to  the Atlantic Ocean, ending weeks of silence about the fate of a  ship which has intrigued European maritime authorities.

Limited information from Russian officials has failed to  satisfy sceptics who voiced doubts about whether the piracy  actually took place or was a convenient cover story to conceal a  possible secret cargo of arms or nuclear material.