Ukraine’s embattled president has issued a call to foreign nationals who are “friends of peace and democracy” to travel to the country to fight against the Russian invasion. The appeal from Volodymyr Zelenskiy, published on the Ukrainian presidency’s website early on Sunday, said the Ukrainian armed forces were in the process of setting up a foreign legion unit for international volunteers. “This is the beginning of a war against Europe, against European structures, against democracy, against basic human rights, against a global order of law, rules and peaceful coexistence,” the statement said. “Anyone who wants to join the defence of Ukraine, Europe and the world can come and fight side by side with the Ukrainians against the Russian war criminals.” The call was repeated on Twitter by Ukraine’s foreign minister, Dmytro Kuleba, and was expected to be the focus of his briefing for international media on Sunday afternoon. Interested volunteers have been told to contact the defence attache of the Ukrainian embassies in their home countries. According to a 2016 decree, foreigners had the right to join the Ukrainian army for military service on a voluntary basis, Zelenskiy’s statement said. Sunday’s appeal by a sovereign government for foreign reinforcements – reminiscent of international involvement in the Spanish civil war of the 1930s – is unprecedented in modern warfare. The UN says the three-day-old Russian invasion on multiple axes has already claimed 64 civilian lives. Russian ground forces have not advanced as quickly as feared, but fierce street fighting and aerial bombardment is under way in both the capital, Kyiv, and the country’s second-largest city, Kharkiv. The world’s media has been flooded by images of Ukrainian citizens preparing molotov cocktails in plastic bottles and learning how to use light arms as their only defences against the might of one of the world’s strongest armies. Poland’s Border Guard said on Sunday that some 22,000 people have crossed from Polish territory into Ukraine since Thursday. “We have to defend our homeland. Who else if not us,” one man in a group of 20 Ukrainian truck drivers waiting to cross at the Medyka checkpoint told the Associated Press. “The Russians should be afraid. We are not afraid,” another man in the group said. They did not give their names, citing their security and that of their families. Poorly sourced “combat tips” and offers to pay for flights have been circulating on a Reddit forum called “volunteersForUkraine”, where the announcement that Zelenskiy is creating a foreign legion was met with enthusiasm. “I just got out of active duty a few months ago. I plan to sell my car Monday and use the funds to purchase equipment and my plane ticket to krakow. From there I’ll find a way to the Ukrainian border,” posted one user, who claimed to be a US air force veteran from California. “To any of you with no combat experience like myself … Be prepared to not come back. I’ve accepted the fact that I’m going to die eventually. If it’s gonna happen at least it’ll be towards a cause I believe in.” The UK foreign secretary, Liz Truss, said on Sunday that Britons who chose to go to Ukraine to fight would “absolutely” have her support. The remarks stand in contrast to the UK position on the war in Syria, where UK nationals who have travelled to fight either for or against Islamic State have faced prosecution on their return home. A small but growing number of Ukrainians living in the UK have made plans to go back to resist the invasion, including veterans of the war with Russia since 2014, community leaders told the Guardian earlier this week. On Saturday, the Ukrainian embassy in Israel also issued a specific callout for volunteers willing to fight on Kyiv’s behalf. In a Facebook post that was later deleted, the embassy asked people who “are ready to defend the sovereignty of Ukraine” to submit their personal details and a description of their military expertise in order to be contacted regarding opportunities to serve. Ukraine is home to at least 43,000 people who self-identify as Jewish and tens of thousands more with Jewish ancestry, making it one of the world’s biggest Jewish communities. About 1 million Ukrainian Jews were killed in the Holocaust, and 80% of the remaining Jewish population of 500,000 is believed to have migrated to Israel after the collapse of the Soviet Union in 1989, meaning that for many in Israel, the new war resonates deeply. The Ukrainian embassy in Tel Aviv did not respond to a request for information about how many people have signed up, but one Israel Defence Forces (IDF) soldier told the Walla news website on Sunday he was planning to fight in Ukraine after his demobilisation. “I came across the post and I couldn’t remain indifferent to what’s happening to the country that my grandfather, grandmother and parents lived in, a beautiful country that I toured less than three years ago,” said the soldier, who was identified as L. “The footage coming out of there has left me frustrated … I felt a burning desire to help.” Another Israeli who took part in an anti-war protest in central Tel Aviv on Saturday night and gave his name as Vladimir told Israel’s Channel 13 News that his 10-month-old daughter was still in Ukraine and he was prepared to join the Ukrainian army to protect his family. Israel had budgeted 10m NIS (£2.31m) for helping Jewish Ukrainian refugees and protecting Jewish institutions in the country, the defence ministry said. Preparations were being made for a new wave of immigration from Ukraine to Israel of 10,000-15,000 people in the coming weeks.