Australia terrorism alert level was raised from medium to high by Prime Minister Tony Abbott during an announcement on Friday. According to multiple reports, the change to the Australia terrorism alert level is the first such change in 11 years.

According to Australia's National Terrorism Public Alert System, the Australia terrorism alert level has been a medium since 2003, during which the four-level system was also introduced.

The Australia terrorism alert level change came two weeks after the UK also raised its terrorism threat level, and a day after the US detailed its strategy in targeting Islamic State (Isis) militants in northern Iraq and Syria, reports The Guardian.

According to the New York Times, the change in the Australia terrorism alert level change also came as security officials warned that there is a growing number of Australians joining extremist groups. He groups that they are taking part in reportedly include the Islamic State in Iraq and Syria.

Earlier in the week, ASIO director-general David Irvine also foretold the news after apparent fears of danger from Australians returning from the battlefields of Syria and Iraq, according to SBS.

Apparently, there are about 60 Australians which agencies believe are joining the fight of terrorist groups in Syria and Iraq. Authorities also believe that about 100 more are giving support to terrorists.

At least 20 Australians have returned from fighting have returned from fighting in the bloody conflicts.

According to The Guardian, on Friday, Abbott also told reporters that the Australia terrorism alert level adjustment was decided upon on the basis of preserving public safety.

Abbott also said that the change to the Australia terrorism alert level had already been executed by the Australian Security Intelligence Organisation (Asio) Thursday night.

There is no evidence suggesting that there is imminent threat, but Abbott said still is "a body of evidence that points to the increased likelihood of a terrorist attack in Australia."

According to Abbott, the increased Australia terrorism alert level would not affect the daily activities of Australians.

Speaking next to Asio director general, David Irvine, Abbott told of the Australia terrorism alert level rise, "I want to stress that this does not mean that a terror attack is imminent."

"We have no specific intelligence of particular plots. What we do have is intelligence that there are people with the intent and the capability to mount attacks. I want to stress that," he added.

The prime minister reportedly said that a "modest public information campaign" is due to begin in the coming weeks. Meanwhile, a hotline was provided to the public to report if there is any case of suspicious activity.

There are no measures specified by Abbott regarding government actions in connection to the Australia terrorism alert level change. However, Abbott said security and border protection agencies would now be getting "the resources and powers they need to detect terrorist activities at home and prevent radicalized foreign fighters from returning to Australia."

However, he did add that there would be increased security in locations such as ports, airports, military bases, power stations and government buildings.

During the Friday announcement regarding the Australia terrorism alert level change, the public has also been assured that there would be no significant changes in police operations.

According to the NY Times, the Australian government announced before that they would be spending about $570 million for expanded counterterrorism measures. Measures include security checks which can prevent Australians from leaving the country to join the bloody conflict in Syria and Iraq.

The Australia terrorism alert levels range from least severe level "low", to top level "extreme". "Low" reportedly indicates that a terrorist attack is not expected. "Medium" means a terrorist attack "could occur". "High", which was to be the current range, means a terrorist attack "is likely". The top level "extreme" reportedly indicates an attack "is imminent or has occurred".

Meanwhile, Australia has currently affirmed support to the US and its willingness to join the country in air strikes in Iraq, or providing provisions for military advisers. The decision came after U.S. President Barack Obama said he would be enlisting a "broad coalition of partners" in targeting Isis militants.

Australia terrorism alert level rise has been denied by Abbott as a decision linked to supporting a US-led coalition which plans on destroying the extremist Islamic State group in Syria and Iraq.