SYDNEY (Reuters) - The head of Australia's national security agency said he was "very seriously" considering raising the country's terrorism alert level to "high" due to the involvement of Australians in militant groups and the spiraling conflicts in Iraq and Syria.
David Irvine, the outgoing head of the Australian Security Intelligence Organisation (ASIO), said the number of Australians returning from fighting with Islamic State and other radical groups posed a growing risk.
Australia has been at the "medium" alert level since a four-tier system was introduced in 2003. A "high" alert level is used when officials believe an attack is likely.
"I would say that, at the moment, it is at a very elevated level of medium and I'm certainly contemplating very seriously the notion of lifting it higher," Irvine told the Australian Broadcasting Corp. late on Tuesday.
Last month, Australia unveiled counter-terrorism measures aimed at preventing young people from becoming radicalized and going to fight in overseas conflicts such as Iraq and Syria.
Irvine said security agencies were aware of at least 20 people who had returned to Australia after fighting in the Middle East, posing a national security risk. Up to 160 people have either been involved in the fighting or actively supporting it, according to Australian officials.
Australia has also joined a multinational relief effort, dropping military equipment and aid to Kurdish forces fighting Islamic State militants in northern Iraq.
Prime Minister Tony Abbott has refused to rule out participating in air strikes or sending combat troops as part of a U.S-led effort to defeat Islamic State.
In August, Britain raised its terrorism alert to the second-highest level, with Prime Minister David Cameron saying Islamic State posed a serious security threat.
Reporting by Lincoln Feast; Editing by Paul Tait