Canberra, AP—A man was shot dead and two counter-terrorism police were stabbed in a confrontation in Australia’s second largest city on Tuesday, police said.

It was not immediately clear whether the violence was related to a recent call from the Islamic State of Iraq and Syria (ISIS) group to supporters to kill in their home countries. But police said the man appeared to be acting alone.

An Australian Federal Police officer and a Victoria state police officer, who were part of a Joint Counter Terrorism Team, had asked the 18-year-old man to come to a police station in southeast Melbourne in relation to a routine matter in an investigation when the violence erupted, Victoria state police Assistant Commissioner Luke Cornelius said.

The two police officers were stabbed before one of the officers shot the man dead, Cornelius said.

“Our members had no inkling that this individual posed a threat to them and as far as we were concerned, it was going to be an amicable discussion about that individual’s behavior,” Cornelius told reporters.

Both police officers were taken to a hospital and were in stable condition Tuesday night.

“It appears this individual was acting on his own and was not acting in concert with other individuals,” Cornelius said. “It’s our belief at this stage that this is an isolated incident.”

Onlookers said the dead man had been shouting insults about Prime Minister Tony Abbott and the Australian government in general in the moments before he was shot, The Age newspaper reported.

Australian Federal Police Commander Bruce Giles said reports that the deceased man had been flying an ISIS flag were being investigated.

Abbott warned Tuesday that Australians who fight with ISIS in the Middle East will be “jailed for a very long time” when they return home under a proposed law that would make it an offense to simply visit terrorism hot spots abroad.

Abbott’s government is to introduce the proposed law to parliament on Wednesday. The legislation is designed to make it easier to prosecute Australian jihadists when they return home from Middle East battlefields and carries sentences of up to life in prison.

“If you fight with a terrorist group, if you seek to return to this country, as far as this government is concerned, you will be arrested, you will be prosecuted and you will be jailed for a very long time indeed,” Abbott told parliament on Tuesday.

At least 60 Australians were fighting in Iraq and Syria with ISIS and another Al-Qaeda offshoot, Al-Nusra Front, the prime minister said.

He revealed that more than 60 Australian would-be fighters had their passports canceled on secret service advice to prevent them from flying to the Middle East.

Dozens of suspected fighters have already returned to Australia from the battlefields. Security agencies fear they now pose a domestic terrorist threat.

Under current legislation, fighting with terrorists overseas carries a maximum 20-year prison sentence. But few have been charged due to the difficulties in gathering evidence from distant war zones.

Under the proposed law, an Australian would be committing a crime by visiting an area that the foreign minister has designated off-limits.

Attorney General George Brandis said entire countries would not be banned, but specific locations such as the Syrian city of Raqqa, which has become an ISIS stronghold, might be.

According to draft legislation released late Tuesday, entering a so-called declared area would carry a maximum penalty of 10 years in prison. Entering a foreign country with the intention of engaging in hostile activity could incur a life sentence.

The onus would be on an Australian who traveled to a no-go zone to prove that the visit was for an innocuous purpose such as humanitarian work or journalism.

The government rejects criticism that the law would effectively shift the onus of proof from the prosecution under the Australian legal system by requiring defendants to prove they are not terrorists.

Abbott left late Tuesday for New York, where he will attend a United Nations Security Council meeting on the problem of 15,000 foreign fighters who are in Iraq and Syria.