The Department of Foreign Affairs and Trade is investigating reports a Sydney man who is part of a flotilla headed for Gaza has been detained by Greek authorities.
Activists say Michael Coleman was taken by the Greek coastguard after he tried to stop them intercepting the flotilla.
Greek authorities are not allowing boats destined for Gaza to leave from local ports.
The group set sail for Gaza to distribute medicine and children's gifts, despite Greek authorities telling them that boats destined for Gaza are not allowed to leave Greek ports, even though they would be sailing into international waters.
Former New South Wales Greens Upper House MP, Syvia Hale, is on the ship and spoke to ABC radio early this morning.
She said the activists got about eight nautical miles out to sea before they were stopped by the coastguard and towed back to port.
"There are armed soldiers on board and at the dockside there are police cars and coastal guards. We are refusing to leave the boat," she said.
The ABC is trying to contact Ms Hale again to confirm the identity of the Australian being detained.
According to peace activist Jennifer Killen, Sydney man Michael Coleman used a kayak in an attempt to stop coastguards from intercepting the mission.
Ms Killen says she has received an email with the news from Ms Hale.
"Michael prevented the coastguard from giving chase for a short while. Then the coastguard was able to get out to sea and follow the Tahrir - the ship that has the Australians on it - they caught up with them and took over the ship, the soldiers boarded the ship," she said.
Greek authorities have said boats destined for Gaza are not allowed to leave Greek ports - even though they would be sailing into international waters.
It is just over a year since nine activists were killed when Israeli marines stormed another pro-Palestinian flotilla.
Greece offered to ferry the humanitarian aid to the Palestinian Authority on Sunday after imposing the ban on the latest flotilla and arresting the captain of one of the boats.
- ABC/Reuters