An Australian politician under investigation for reportedly joining the civil war in Syria claims to have had 10 years' experience in the army and left behind a wife and three sons when he disappeared several weeks ago.

Matthew Gardiner, 43, switched off his phone and "defriended" most of his friends on Facebook after disappearing from his Northern Territory home.

Matthew Gardiner, a senior figure in the Northern Territory branch of the Labor Party, has reportedly gone to fight in Syria. Credit:ABC TV

He has reportedly joined Kurdish forces fighting against Islamic State in northern Syria.

The Australian Federal Police confirmed they were investigating Mr Gardiner's movements.