President attends second world war commemorations held for first time since Russia took over region from Ukraine

Vladimir Putin has arrived in Crimea as the region holds its first Victory Day commemorations since Russia's takeover.

The day, marking victory over Nazi Germany in the second world war, has become a key display of Russian patriotism. It was marked in Moscow by a military parade in Red Square, where the Russian president had earlier told a crowd of soldiers and war veterans that those who defeated fascism must never be betrayed – a message with a pertinent ring since Moscow has portrayed the interim government in Ukraine as being led by neo-fascists.

Hours before Putin arrived in Crimea, at least three people were killed in clashes between government forces and rebels in the eastern Ukrainian city of Mariupol. Fighting broke out when troops attacked the city's police station which had been seized separatist militiamen. A Guardian reporter saw two dead bodies, one a policeman, lying outside the gutted police station. Ukraine's interior minister, Arsen Avakov,claimed on his Facebook page that security forces had killed about 20 pro-Russia militants.

The patriotism reached fever pitch in Sevastopol before his arrival as Russian fighting vehicles, Putin's favourite biker gang and militiamen who helped Crimea break away from Ukraine paraded through the city.

Tens of thousands of people chanted "Russia!", "Victory!" and "Thank you!" as 1,000 troops, 60 military vehicles, thousands of veterans and other groups marched past over two hours. Putin is expected to watch an air and naval show featuring 70 aircraft, to symbolise the 70th anniversary of Sevastopol's liberation by Soviet forces, which lost more than 200,000 in fighting.

"We're all happy to be part of Russia. Hooray for veterans!" shouted seven-year-old Mikhail Rybak as onlookers cheered him on. "It's good that we got away from Maidan, that we're safe," he added, referring to the Euromaidan demonstrations in Kiev that toppled the Ukrainian president, Viktor Yanukovych, and led to Russia seizing Crimea in March.

A reported 97% of voters chose to join Russia in a subsequent referendum which did not have an option to remain part of Ukraine. The vote was boycotted by most Crimean Tatars, who make up about 15% of the peninsula's population. Sevastopol, where Russia's Black Sea fleet – and previously that of Ukraine – has been based since the breakup of the Soviet Union, is the heart of pro-Russian sentiment in Crimea.

Speaking on Red Square, Putin praised the Soviet Union's fight against fascism, saying: "Our country was the one that beat the Nazis back to their lair … saved Europe from slavery." The Kremlin and Russian media have portrayed the pro-Russia uprising in eastern Ukraine as a similar battle against the "fascist junta" in Kiev, which they argue is dominated by Russophobic ultra-nationalists. Many of those present in Sevastopol echoed this sentiment.

In Kiev, celebrations took place amid tight security, with police reinforced by pro-Ukrainian self-defence groups. The cancellation of a traditional military parade meant the festivities were more modest than usual. Many locals were wearing red poppies rather than the black and orange St George ribbon representing the Soviet Union's victory in the second world war that has been widely worn by anti-Kiev insurgents.

"The St George ribbon is associated with events in the east where they are killing people … traitors wear the St George ribbon," said Galina Prikhodko, 26, who had come to lay flowers near the city's Motherland statue.

There is international concern that Russia could seize parts of eastern Ukraine, where pro-Russia separatists have taken control of several towns and key buildings in the city of Donetsk.

Several thousand people gathered in Donetsk's Lenin Square for the victory celebrations. The mood was heavily influenced by the current situation, with several speakers comparing the victory over the Nazis to the "fascist junta" in Kiev.

The few living second world war veterans on the stage were joined by fighters from the self-proclaimed People's Republic of Donetsk, many of whom were armed with Kalashnikovs, sniper rifles or, in one case, a giant mallet.

Officials said on Friday that the referendum planned for Sunday was not about independence or joining Russia, but merely about giving the region more autonomy. However, speeches from the stage were unequivocal.

"We are Russians, and Russia is our homeland," said Denis Pushilin, the de facto head of the separatist movement. "Russians here are not occupiers. They are our brothers."

Russia has called for the referendum to be postponed.

On Tuesday, the German chancellor, Angela Merkel, called Russia's decision to hold a military parade in Crimea a "shame" given the ongoing crisis in Ukraine, but that did not dampen the patriotic euphoria in Sevastopol on Friday.

Mikhail's mother, Yelena, who said her grandfather had been killed in the second world war, called Putin a wise leader and said the new government in Kiev was discriminating against Russian speakers.

"Seeing all this military equipment, we feel such pride and patriotism, we feel ready to give our lives for our country," she said.

Her husband, Roman, said Crimea joining Russia had given residents "hope in a good, dignified future. Crimea has come into Russia's protection; protection against the fascism and economic changes that await Ukraine."

"Patriotism is in our blood, but now it is waking up," said Mikhail Tkachenko, who was wearing his grandfather's Red Army jacket and said he had previously served in the Ukrainian army. "Freedom is understood differently by everyone. In western Ukraine they understand it differently than we do here."

A huge variety of civilian groups also took part in the parade, from battle re-enactors to local self-defence militias, and the Night Wolves, a biker gang whose leader Alexander "Surgeon" Zaldostanov is a personal friend of Putin. One member of the gang who would only give his nickname, Scythian, said he had come from the Volga river city of Saratov to celebrate the "special holiday" in Sevastopol. He said he hoped south-eastern Ukraine would be the next region to join Russia.

"I'm for the Soviet Union. I'd like all the former republics to rejoin," he said.

Dozens of Cossacks, the historical military caste that has been making a comeback in southern Russia, also marched in the parade. "All of Ukraine will soon be ours. We need to fight the Bandera supporters and Jews who have come to power in Kiev," said Viktor, who hoped he and his fellow Cossacks would soon have the same policing duties as their brethren in Russia.

Yevgeny Vakulenko, a member of the Rubezh self-defence militia, said he had manned a checkpoint outside the city during the occupation of Crimea by Russian troops and local volunteers.

He said that as part of Russia, Sevastopol would see "a flowering of the city, complete reconstruction. As part of Ukraine the city was on the brink of poverty."

The dream of a reunited USSR was shared by Valentin Volenkov, a 27-year veteran of the Soviet air force who was gathering bouquets and cards given in gratitude by passersby. "What is one finger on its own? It's weak. But five fingers together are a fist," he said. "I'm glad Belarus and Kazakhstan didn't leave us," he added, referring to the customs union that Putin has promoted as a Russian-led potential rival to the European Union.

As an accordion player, Volenkov said he loved Ukrainian songs, "but because of a few idiots in power we had to split up with our friends".

The Russian deputy prime minister, Dmitry Rogozin, was meanwhile at a parade in the breakaway Transnistria region of Moldova, where Russia has stationed troops since 1990. He told a crowd of 2,000 that "the plague of fascism is thriving" and referred specifically to the deaths of mainly pro-Russians in Odessa, Ukraine, last week.