Australia's government on Thursday approved legislation that strengthens the country's terrorism laws by allowing convicted terrorists to be held without charge after serving a prison sentence.

Under the legislation, the attorney general may ask a court to indefinitely detain a convicted terrorist 12 months before their sentence expires on the grounds that the convict would pose an unacceptable risk of committing an act of terrorism upon release.

The Supreme Court would then have to approve the extended detention given the risk of the prisoner committing a serious terror offense after being freed.

"This bill strengthens the ability of our security agencies to continue to detain somebody if they've committed serious terrorism offenses … and they have not been rehabilitated," said Australian Justice Minister Michael Keenan.

"We are not going to allow people who haven't been rehabilitated in prison to be released and then go on to harm our fellow Australians," he added.

Opposition lashes out

However, the new law was met with criticism by the Greens party and Liberal Democrat David Leyonhjel, who argued that the legislation undermines civil liberties in Australia.

"We should not be able to effectively impose life imprisonment on someone who was not originally sentenced to life imprisonment," Leyonhjelm said.

The legislation comes amid an increase in counter-terrorism operations across the country, which resulted in criminal charges against 55 people.

In September 2014, Australia raised its terror alert level to high amid fears that citizens who fought alongside the "Islamic State" militant group may return to the country.

At least 40 people are being prosecuted and 17 others imprisoned on terrorism charges, according to the justice ministry.

ls/kl (AFP, dpa)