NORFOLK, Va. - A man accused of negotiating on behalf of Somali pirates in the deadly hijacking of a U.S. yacht has been indicted on charges he successfully negotiated the ransom for a German tanker and its 22 crewmembers, the government said Thursday.

The accused, Mohammad Saali Shibin, is the biggest catch in the U.S. prosecution of pirates plaguing shipping lanes off the coast of Africa, U.S. Attorney Neil H. MacBride said outside the federal courthouse in Norfolk.

"Mr. Shibin is alleged to be among the select few who are entrusted with one of the most important tasks in Somali piracy -- ensuring a ship's owners pay the maximum amount of ransom possible for the release of a hijacked vessel," McBride said.

Shibin, already in U.S. custody for his alleged role in the deaths of four Americans on the yacht Quest earlier this year, is multilingual and is technologically savvy -- skills needed to assess a ship's value and to serve as a go-between, McBride said.

The chemical tanker Marida Marguerite and its crew of 22 aboard was hijacked in May 2010 and held off the coast of Africa for seven months until a ransom believed to total millions was paid to the pirates. All 22 crewmembers survived.

Shibin was paid $30,000 to $50,000 for his alleged services, according to the indictment, which is dated Wednesday.

The superseding indictment, which includes previous charges related to the Quest hijacking, accuses him of piracy, hostage taking, violence against maritime navigation, conspiracy and firearms violations.

His arraignment is scheduled Wednesday. His attorney did not immediately return a telephone message left by The Associated Press.