The global call has split opinion over whether travellers could breach laws in their home countries when signing up for a foreign conflict,although the United Kingdom Foreign Secretary Liz Truss said she “absolutely” supported citizens who wanted to support Ukraine.

Mr Morrison said the situation was “complicated” and the issue would be on the agenda for the national security committee of federal cabinet when it met on Tuesday.

“Our law sets out arrangements where people can be involved in official activity by a sovereign state,which Ukraine qualifies,but the nature of these arrangements are very uncertain,and I would stress this,our travel advice to all Australians is do not travel[to Ukraine],” Mr Morrison said.

“So let me be very clear about that. That is the Australian government’s advice for all Australians not to travel to Ukraine for obvious reasons.

“I can understand absolutely the strong feelings and the motivations for people to go and do that. But I would say at this time,the legality of such actions are uncertain under Australian law.”

The national security committee will also decide on Tuesday how much money to give to NATO to buy weapons for Ukraine,with the total likely to be in the millions of dollars.

The chairman of the Australian Federation of Ukrainian Organisations,Stefan Romaniw,said he spoke to Australian federal ministers on Sunday about whether it was legal to sign up for a foreign war,given his understanding that it was illegal to join a conflict as a mercenary.

“The problem would not be getting in but it might be a problem getting out,” he said of travelling to the conflict.

Romaniw said he did not know of anyone who had flown to Ukraine to join the fight but Ukraine’s charge d’Affaires in Canberra,Volodymyr Shalkivskyi,said he had been approached by Australians who were willing to fly to the war zone to join the Ukrainian forces.

“Yes,I can confirm we have a number of requests from different Australians,” Shalkivskyi toldThe Sydney Morning Herald andThe Age on Sunday night.

“It’s a very serious question so it’s not about going for adventure. I want to facilitate this but I do not want these people to violate Australian legislation.”

The Ukraine embassy plans to consider the law in talks with the Australian government before taking any further steps.

Danish Prime Minister Mette Frederiksen said on Sunday it was a choice “anyone can make” and this covered Ukrainians living in her country as well as others who thought they could contribute.

“There is nothing at first sight that would legally prevent someone from going to Ukraine to participate in the conflict,on the Ukrainian side,” she said.

Truss triggered a debate in the UK,however,when she told the BBC she would support people who chose to side with Ukraine.

“The people of Ukraine are fighting for freedom and democracy,not just for Ukraine,but for the whole of Europe. Absolutely,if people want to support that struggle,I would support them in doing that,” she said.

But Dominic Grieve,a former attorney-general in Britain under conservative leader David Cameron,toldThe Guardian Britons who fought in Ukraine would be in breach of a law passed in 1870 that made it illegal to enlist in a foreign army at war with a country at peace with Britain.

Grieve said the comments from Truss were “honourable” but people would break the Foreign Enlistment Act unless the government gave them formal approval to go to Ukraine to fight.

A spokesman for the Australian Minister for Foreign Affairs,Marise Payne,said “the Foreign Incursions Act prohibits going overseas to fight unless it is for a properly constituted national armed forces”.

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