BRUSSELS - The European Commission expressed doubt on Friday over whether a merchant ship which has been missing for more than a week had fallen prey to pirates as the vessel's operator had suggested.

Its remarks added to the deepening mystery over the 4,000-tonne Arctic Sea, whose disappearance has baffled authorities across Europe and North Africa and prompted the Kremlin to send Russian warships to join the hunt.

Radio calls were apparently received from the ship which had supposedly been under attack twice, the first time off the Swedish coast then off the Portuguese coast, a spokesman for the executive arm of the European Union told journalists.

From information currently available it would seem that these acts, such as they have been reported, have nothing in common with traditional acts of piracy or armed robbery at sea, Martin Selmayr said.

The Maltese-registered vessel, carrying a $1.3-million cargo of timber and a Russian crew, was supposed to have docked on August 4 in the Algerian port of Bejaia. It never arrived and is thought to have last made contact from the Atlantic Ocean off the coast of France.

A wave of piracy has hit shipping off Somalia, and an international naval force patrols its coast in an effort to protect merchant vessels. But a hijacking in European waters would be almost unprecedented in modern times.

Concerns over the safety of the 15-member Russian crew were raised after the Malta Maritime Authority said it received reports the ship had been boarded by armed men in masks posing as anti-drugs police in Swedish waters on July 24.

Russia's navy denied a report on state television that the frigate Ladny was following a ship of a similar description in the Atlantic Ocean not far from Gibraltar.

Relatives of the crew appealed to Prime Minister Vladimir Putin in an open letter and demanded a criminal investigation into the vessel's disappearance, Russian media reported, but have now stopped speaking publicly about the case.

(Reporting by David Brunnstrom; writing by John O'Donnell; editing by Tim Pearce)

Somalia