Canberra, April 7 (IANS): A former official from Australia's Labour Party, who is believed to have fought for Kurdish forces against the Islamic State (IS), should be investigated, the leader of opposition said on Tuesday.

Former president of Northern Territory's Labour Party, Matthew Gardiner was detained for questioning upon his arrival on Sunday at the Darwin airport after spending several months abroad where he was suspected of fighting with Kurdish forces in the Middle East, Xinhua reported.

Leader of Opposition Bill Shorten said Australians who visited the prohibited areas of Syria and Iraq should be thoroughly investigated.

Shorten said the Australian Federal Police should investigate anyone who travelled to the zones.

"We say to any Australian who thinks they should take part in these conflict zones, don't do it. And if you return, the police will appropriately investigate the matter consistent with the law," he said.