Foreign Minister Bob Carr welcomed news that Australian man Warren Rodwell was alive after being held hostage for more than a year in the Philippines, but said his prolonged captivity was a "major concern".
Rodwell, a 54-year-old former soldier from Sydney, was seized by suspected Muslim extremists from his home in the southern Philippine town of Ipil on December 5, 2011.
In a video the SITE monitoring group said had been posted on a YouTube channel linked to Abu Sayyaf, Rodwell confirms he was captured by that militant group, which was founded in the late 1990s with seed money from Al-Qaeda.
Rodwell says the date is December 16, 2012 and holds up a newspaper from the previous day. He says he was kidnapped 54 weeks ago.
"I'm being held prisoner, kidnapped by (the) Abu Sayyaf Muslim terrorist group for over one year -- actually 53, 54 weeks today," Rodwell says in the two-minute video.
"This video clip today is to say that I am alive, I am waiting to be released. I have no idea what's going on outside, I'm just kept held prisoner in isolation."
Carr on Thursday said the "confirmation of Mr Rodwell's welfare is welcome" but described his prolonged captivity as a "major concern".
"The Philippines government has the lead in response to this case and is devoting significant resources to securing Mr Rodwell's release," Carr said in a statement.
"The Australian government is assisting Philippines authorities where appropriate."
Carr said government officials were also in regular contact with Rodwell's family and it would "not be helpful to Mr Rodwell to comment further".
The Philippines military said it was working to verify whether the video was legitimate.
"The Armed Forces of the Philippines will take measures in support to the Philippine National Police... to fully ascertain the identity and if possible, the whereabouts of the individual if he is a kidnap victim," said Major Emmanuel Garcia, the military's deputy chief for public affairs.
Rodwell last appeared in a video in May that was believed to be dated from the end of March.
In another video in January, reportedly sent to his Filipina wife Miraflor Gutang, Rodwell said his captors were demanding US$2 million in ransom.
Numerous armed Islamist groups operate in the southern Philippines, spawned by a bloody Muslim separatist insurgency that has raged for decades.
Abu Sayyaf has been blamed for the worst terror attacks in Philippine history and has previously kidnapped foreigners and Christians for ransom.