THE head of the al-Qaida cell that beheaded an American engineer justified the killing in a message written before he himself was shot dead by Saudi security forces.

Islamic militants who claim to have abducted an American in Saudi Arabia are threatening to torture him in the same way as Iraqi inmates were mistreated in a US-run prison in Baghdad.

Suspected militants have shot dead an American as he parked his car in the garage of his home in the Saudi capital.