Five American Muslims from the Washington area who went missing have been detained in Pakistan as US authorities were investigating their motive for leaving the country, US officials and a Muslim group said.

The five men in their 20s from northern Virginia are believed to have travelled to Pakistan as a group. One of them left behind a videotape that appeared to be a "farewell" statement accompanied by references to the conflict between the West and Muslim world, Nihad Awad, executive director of the Council on American-Islamic Relations (CAIR), told reporters Wednesday.