"Like many other countries, Australia is dealing with an increased terror threat," said Abbott, in a video message released early on Sunday.
"Since the terror alert level was raised from medium to high last September, we've witnessed terrorist inspired events in Sydney and in Melbourne," said Abbott, adding that a further six terrorist attacks have been averted by security forces.
"Australia faces a growing challenge from foreign fighters, and from home-grown terrorists. At least 250 Australians, some very young, have become ensnared in the evil ideology of the Daesh death cult."
"If you survive and seek to return, expect to face the consequences. You will face the full force of the law."
"In coming days the government will be making further announcements about keeping our country as safe as possible. You can be assured that this government will do everything in our power to protect our people, and to stop radicalized and brutalized people from roaming our streets."
The announcement was released before the Australian government unveils new legislation in parliament this week, which is expected to include laws to tackle the terrorist threat.
Last week the Australian media reported that one of the measures is to make changes to Australia's Citizenship Act, allowing second generation Australians who are caught supporting a terror to be stripped of their citizenship.
Immigration spokesman for the opposition Labor Party Richard Marles told the Australian media on Sunday that instead of departing Australians with dual nationality, national security interests would be better served by jailing jihadists.
"I make the observation that the safest place for someone who means to do our country harm is in an Australian prison," said Marles, whose party leader Bill Shorton earlier promised bipartisan support for government initiatives to deal with terrorism.
