Australian leaders have condemned terrorist attacks in Brussels which have killed at least 31 and wounded 250, although authorities have not determined if any Australians have been affected.

The terrorist attacks consisted of two bomb explosions at Zaventem airport and one in Maelbeek. Islamic State has claimed responsibility for the attack through its media wing, but its claim of responsibility has not yet been formally verified.

The foreign affairs minister, Julie Bishop, said in a statement: “The Australian government condemns the coordinated terror attacks on 22 March in Belgium. Our thoughts and sympathies are with the people of Belgium.”

“The Department of Foreign Affairs and Trade (Dfat) is urgently seeking to determine whether any Australians have been affected.

“I understand Belgian authorities have activated their emergency plan in response to these attacks and increased the national threat level to its maximum level,” she said.

The prime minister, Malcolm Turnbull, said: “All Australians condemn these cowardly terrorist attacks in Brussels. And the Belgian people have our thoughts, our prayers and our resolute solidarity in this battle against terrorism.

“They are utterly cowardly attacks, attacking innocent people, but we need to be constantly vigilant, vigilance is the key.”

Turnbull confirmed at 7.50am on 23 March that “so far we have no news of Australians being killed or injured”.

Turnbull said Australia was in a stronger security position than Europe because the country has “strong border protection”, with fewer porous borders, and “a much greater insight into people who we would regard as being threats or likely to pose a risk to safety of Australians”.

The government has upgraded travel advice for Belgium, advising Australian travellers to reconsider their need to travel.

“Australians in Brussels should remain attentive to their surroundings, avoid affected areas and follow the instructions of local authorities,” Bishop said.

“I have spoken with our ambassador Dr Mark Higgie for an assessment of the situation and confirmation that our embassy staff and their families are safe.”

The opposition leader, Bill Shorten, labelled the events “shocking and distressing”.

These are shocking and distressing events unfolding in Brussels. Australian hearts go out to all those who live in this great city. — Bill Shorten (@billshortenmp) March 22, 2016

Former prime minister Tony Abbott described the event as a “dreadful atrocity” and added “killing people in the name of God is simply evil”.

A dreadful atrocity. Killing people in the name of of God is simply evil. All our thoughts and prayers must be with the people of Brussels. — Tony Abbott (@TonyAbbottMHR) March 22, 2016

Former prime minister Julia Gillard described the attacks as horrifying and “an assault on fundamental human values”.



The Brussels attacks are horrifying-an assault on fundamental human values. We all mourn with the people of Brussels and stand with them-JG — Julia Gillard (@JuliaGillard) March 22, 2016

The attorney general, George Brandis, told ABC radio that terror alert levels were always under review but “at the moment, the Australian terror alert level remains at probable, which is where it has been since September of 2014”.

Brandis said since September 2014 there had been three individual terrorist events in Australia which were all “lone wolf” attacks. “During the same period, we have disrupted six other imminent terrorist events,” he said.

The Community and Public Sector Union (CPSU) announced on Wednesday morning it would postpone strike action by immigration and Australian Border Force staff at international airports until at least Easter Monday.

The decision was made after Turnbull, in response to Brussels terrorist attacks, called on union members not to strike because of security concerns.

The CPSU had planned a 24-hour strike on Easter Thursday, 24 March, and a series of rolling stoppages on 23 March and from 25 March until 4 April. The union has not decided yet whether the suspension will extend beyond Monday 28 March or stoppages will resume.

Bishop advised that Australians concerned about the welfare of family and friends in the region should attempt to contact them directly.

If unable to contact loved ones, Australians were advised to call the Dfat 24-hour consular emergency centre on 1300 555 135 or +61 2 6261 3305 if calling from overseas.