Poland has tens of thousands of Ukrainian men of military age on its territory, according to UN figures.

Ukraine is scrambling to recruit troops after more than two years of war and has recently passed a mobilisation law, lowering the fighting age and toughening penalties against draft dodgers.

Late Wednesday it said it would stop issuing new passports abroad to some military-aged men under the new legislation.

It has also suspended consular services for men aged 18 to 60 living abroad, sparking fury among expatriates in Poland and elsewhere.

Polish Defence Minister Wladyslaw Kosiniak-Kamysz said late Wednesday that Warsaw could help in getting military-aged men back to Ukraine.

"We have suggested for a long time that we can help the Ukrainian side ensure that people subject to compulsive military service go to Ukraine," he told Polsat television.

"Everything is possible," he said when asked if Warsaw would agree if Ukraine asked for people subject to the draft be transported to Ukraine.

On Thursday, his Lithuanian counterpart Laurynas Kasciunas said the authorities in Vilnius could follow Poland's moves.

"I think this is the right way," Kasciunas told reporters, referring to the Polish minister's remarks.

"Ukraine is very short of mobilisation reserve... This is not fair to those citizens who are fighting for their country," Kasciunas said.

"We don't have that many such people in Lithuania. But we do have a small number," he said, without providing specific numbers.

After Russia invaded Ukraine in February 2022, hundreds of thousands of Ukrainians fled the war, with most passing through Poland.

As of February this year, 952,104 Ukrainian refugees were registered in Poland, of whom 16 percent, or 152,656 people, were of military age, according to the UN refugee agency UNHCR.

But many Ukrainians were also in Poland before the outbreak of the war.

Lithuania, according to its migration office, hosts over 74,000 Ukrainian citizens, with more than half of them moving to the country after Russia's invasion in February 2022.