WASHINGTON (REUTERS) - A US federal grand jury has indicted a Saudi-born man accused of being an Al-Qaeda operative who conspired to attack American soldiers in Afghanistan and diplomats in Nigeria, the Justice Department said on Wednesday.

Ibrahim Suleiman Adnan Adam Harun, also known as "Spin Ghul," was indicted on conspiracy charges in February 2012 after extradition from Italy, but the charges were unsealed only on Wednesday, the department said.

He was born in Saudi Arabia but claims citizenship in Niger, the department said.