The six men, and a group of five other Somalis captured after allegedly firing on another US warship, were brought to Norfolk, Virginia, where they were charged in a US criminal court with the attacks on the vessels.

Lawyers for the six Somalis accused of attacking the USS Ashland argued that the piracy charge should have been dropped because they did not board or take control of the warship or obtain anything of value from it.

The men were also charged with other crimes, including attacking to plunder a vessel, acts of violence against people on a vessel, conspiracy and assault with a dangerous weapon on US officers and employees.

Their trial is due to begin in October.