Pirates have tried to board a Maltese-flagged merchant vessel, 30 miles off Yemen, a Nato official said yesterday.

The 28,693-tonne bulk carrier MV Atlantica was travelling through the Gulf of Aden when two speed-boats approached, Nato Lieutenant Commander Alexandre Fernandes said.

A statement from the Atlantica said each boat had six heavily-armed men. One skiff used a ladder to try to board the vessel and another shot at it with automatic weapons, he said.

The bulk carrier escaped by increasing speed and using other unspecified anti-piracy measures, Lieutenant Fernandes said.

Later, Somali pirates released a Togo-flagged cargo ship seized last week, a UN aid agency said yesterday. The nearly 5,000-tonne MV Sea Horse was on its way to pick up food for the aid group when it was hijacked. A pirate source said a $100,000 (€77,400) ransom was paid.

Pirates have made millions of dollars in ransoms hijacking commercial vessels in the busy shipping lanes of the Gulf of Aden and Indian Ocean, despite patrols by foreign navies off the Somali coast.