RICHMOND, Va. (AP) — Piracy charges against six Somali nationals should be dismissed because the defendants did not take over or rob the U.S. Navy ship they are accused of attacking, lawyers for the men argue.

The defendants are being held for trial in Norfolk on piracy and other charges related to an April 10 attack on the USS Ashland in the Gulf of Aden off Somalia’s pirate-infested coast. Their skiff was destroyed during the encounter.

‘‘The parties dispute what prompted the USS Ashland to destroy the small vessel,’’ the attorneys argued in a motion filed in U.S. District Court in Norfolk. ‘‘But there is absolutely no dispute that the defendants did not take control of the USS Ashland, did not board her, and did not successfully obtain anything of value from her.’’

The motion cites an 1820 court case that defines piracy as the seizing and robbing of a vessel at sea. The attorneys said there is no evidence the six men took control of or robbed the ship.

The government said Thursday it would respond to the motion in court.

The six defendants accused in the attack on the amphibious dock landing ship are among 11 Somali men captured by the Navy off the coast of Africa. Five were caught March 31 after the frigate USS Nicholas exchanged fire with a suspected pirate vessel west of the Seychelles.

Each man is charged with piracy, attacks to plunder a vessel, assault with a dangerous weapon and other weapons counts. Piracy carries a mandatory life sentence. All 11 have pleaded not guilty.

The Ashland and Nicholas, both based in Virginia within 20 miles of the courthouse, were part of an international flotilla protecting shipping in the region.

The 11 had been held on U.S. ships for weeks as officials decided whether and where they could be prosecuted. They settled on Norfolk.

The motion to dismiss was among several filed by a Wednesday deadline. One attorney also asked to move the trial, saying a fair jury couldn’t be seated in the Navy town of Norfolk. Another states the men who were in the skiff destroyed by the Ashland were ferrying refugees and were not engaged in piracy.

In a separate filing posted electronically Thursday, lawyers for the Ashland defendants seek dismissal based on destruction of evidence: crew members destroyed the skiff that carried the accused with 25mm rounds.

Attorneys for the six said the skiff, which sank, contained ‘‘serious exculpatory value.’’ That evidence was not detailed in the filing.

The six accused in the Ashland attack are scheduled to be tried Oct. 19. The trial of the accused Nicholas pirates is scheduled to begin Sept. 8, also in Norfolk.

The defendants are being held in a regional jail outside Norfolk.