SEVASTOPOL: President Vladimir Putin took a victory lap Friday in his first visit to Crimea since its annexation by Russia, as fighting in eastern Ukraine left more than 20 dead just days ahead of a separatist vote.

The visit drew a sharp rebuke from authorities in Kiev, who accused the Russian strongman of stoking tensions with his visit to Sevastopol, home to Russia's Black Sea fleet.

“This provocation once again confirms that Russia deliberately seeks further escalation of tensions,” the foreign ministry said, calling the visit a “flagrant violation of Ukraine's sovereignty”.

The White House also condemned the trip, with National Security Council spokesman Laura Magnuson saying it “will only serve to fuel tensions”.

With unease high ahead of an independence vote planned for Sunday in parts of eastern Ukraine, fighting between Ukrainian troops and pro-Moscow militants erupted in the southeastern port city of Mariupol.

An attempt by around 60 rebels armed with automatic weapons to storm the city's police headquarters turned into a “full-scale military clash” when army and interior ministry troop reinforcements arrived, Interior Minister Arsen Avakov said on his official Facebook page.

He said the death toll from the near-two-hour combat stood at 20 rebels and one policeman, while another four policemen were wounded and four rebels were captured.

Witnesses in Mariupol told AFP the fighting was ferocious and involved an exchange of automatic gunfire and shelling from eight armoured vehicles.

The police headquarters was gutted by fire and, after the battle, firemen were at the scene trying to extinguish the flames.

'Awful lot of shooting'

“There was an awful lot of shooting,” said an eyewitness who gave his first name as Aleksandr.

In Sevastopol, Putin reviewed Russian ships in the bay, hailing the sailors on board with a “Hello comrades!” as he congratulated them on Friday's 69th anniversary of the Soviet victory over the Nazis in World War II.

Putin said 2014 “will go down in history” as the year when the “historic truth” of Crimea as part of Russia was recognised.

“Much work remains ahead, but we will overcome all difficulties... because we are together. And that means we are even stronger,” Putin told a cheering crowd.

Russia's annexation of Crimea in March set off the worst diplomatic crisis in the West's relations with Moscow since the end of the Cold War.

It has been followed by uprisings and fighting in eastern Ukraine that have raised concerns of a civil war erupting on Europe's doorstep.

Despite a surprise call from Putin this week to delay independence referendums, rebels holed up in more than a dozen towns and cities in eastern Ukraine vowed to press ahead with votes this Sunday that are bound to increase tensions.

Putin flew to Sevastopol after overseeing the traditional Victory Day parade in Moscow's Red Square.

Addressing some 11,000 troops who marched alongside tanks, armoured vehicles and mobile missile systems, Putin hailed Russia's “all-conquering patriotic force”.

The Soviet Union's victory over Nazi Germany 69 years ago has long been a source of great pride throughout the ex-USSR, which lost some 30 million citizens during World War II.

In contrast to the display of military hardware on Red Square, Ukraine held muted Victory Day celebrations in a bid to avoid violence.

The head of Kiev's city council banned large-scale public gatherings or parades in the capital, fearing that the veterans could be attacked by “Russian provocateurs”.

A short ceremony was held in the presence of Prime Minister Arseniy Yatsenyuk, several former presidents and a few dozen veterans in the city's main park.

Their chests bulging with medals, the veterans marched with flowers in their hands but the atmosphere was subdued.

“Today's celebration has been ruined. We cannot celebrate the victory as usual because of the political situation,” said one of the veterans, Vasyl Kupchenko.

Previous violence in Ukraine in recent weeks saw 14 troops killed, three helicopter gunships downed and 66 servicemen injured in assaults on the rebels.

The fighting also claimed the lives of more than 30 insurgents.

Clashes that resulted in a horrific inferno in the southern port city of Odessa last week claimed another 42 lives, most of them pro-Russian activists.

Unrest was also reported Friday in the eastern city of Donetsk, with pro-Russian militants saying two of their number were wounded by brief gunfire from Ukrainian troops stationed at a sanatorium on the outskirts of the city.

The troops withdrew from the area after talks, they said.

The Ukrainian prosecutor's office said it was also investigating the death of an Orthodox priest allegedly shot eight times at a rebel checkpoint in the Donetsk region on Thursday.

The crisis in Ukraine kicked off after the ouster of the country's pro-Kremlin president Viktor Yanukovych in February.