Australia and Iran will share intelligence to track foreign fighters working with the Islamic State group in Iraq, Foreign Minister Julie Bishop said Monday, as lawmakers urged caution.

In the first trip to Iran by an Australian minister in more than a decade, Bishop said it would be an informal arrangement.

Australian Prime Minister Tony Abbott said Monday that he will use a trip to Turkey for Anzac Day commemorations to push Ankara for increased security on its border with Syria and Iraq.

The border is one of the preferred routes for foreign fighters seeking to join Islamic State (IS) jihadists, with Western powers criticising Turkey for not doing enough to seal it off.

Iran is not willing to accept its nationals being forcibly deported from Australia but will welcome back citizens of their own free will, a top official warned Sunday.

The remarks by deputy foreign minister Hassan Ghashgavi came as Australian Foreign Minister Julie Bishop visited Tehran but failed to make a breakthrough on a long-running immigration dispute.

A 39-year-old Lebanese national was killed at dawn in Melbourne, Australia after unknown assailants opened fire at him.

The state-run National News Agency reported on Sunday that Khaled Yehya Abou Hasna was the victim.

Security will be boosted at Anzac Day commemorations in Australia's state of Victoria, as its premier on Sunday urged people to turn up despite arrests linked to an alleged Islamic State-inspired attack plan.

Police arrested five men in counter-terrorism raids in the state's capital Melbourne on Saturday and charged one of them -- 18-year-old Sevdet Besim -- with conspiring to commit a terrorist act on Anzac Day on April 25 when ceremonies are held across the nation to remember fallen Australian and New Zealand Army Corps troops.

Australia's foreign minister on Saturday hailed Iran's efforts to crush the jihadist Islamic State group in Iraq, saying on a rare trip to Tehran that the militants can be defeated.

Julie Bishop is Australia's highest-ranking official to visit Iran in 12 years and she discussed the conflict in Iraq with her Iranian counterpart Mohammad Javad Zarif.

Two men were arrested in Melbourne on Saturday for allegedly planning an Islamic State-inspired attack at Anzac Day commemorations honoring soldiers who fought and died for Australia -- the country's most important national event.

Seven search warrants were executed in the country's second largest city by a joint counter-terrorism team of 200 officers, two months after Prime Minister Tony Abbott warned the threat from home-grown extremists was worsening.

Australia is returning almost 50 Vietnamese asylum-seekers using a warship currently off the Asian nation's coast after intercepting them at sea, a report said Friday, as Canberra enforces a tough immigration policy.

The asylum-seekers were found by customs and navy vessels north of Australia earlier this month before being transferred to amphibious landing ship HMAS Choules, The West Australian newspaper said.

Australian Foreign Minister Julie Bishop visits Iran at the weekend looking for Tehran to take back failed asylum seekers, but the rare trip also has deeper significance as the West seeks to seal a deal to rein in the Islamic state's nuclear ambitions.

The first visit to Shiite Iran by an Australian foreign minister in 12 years follows the framework political agreement reached last month under which Tehran would accept strict nuclear controls in return for the easing of damaging economic sanctions.

The search area for flight MH370 will double in size to encompass a vast Indian Ocean corridor if wreckage remains elusive, Malaysia, Australia and China said Thursday, asserting their commitment to finding the plane.

Meeting in Kuala Lumpur, ministers from the three countries said the deep-sea zone now being scanned for signs of the ill-fated Malaysia Airlines jet would be expanded to 120,000 square kilometers (46,300 square miles) if the current area comes up empty.