President Vladimir Putin flew into Crimea on his first visit to the peninsula since its seizure from Ukraine by Russia.
Mr Putin first addressed crews from Russia's Black Sea fleet on the 69th anniversary of the victory over Nazi Germany in World War II.
Then, speaking to veterans among huge crowds in the port of Sevastopol, Mr Putin said 2014 would be remembered as the year when the Crimean people made a firm choice to be part of Russia.
Russia's President Vladimir Putin (centre) and World War II veterans lay flowers at a war memorial in Sevastopol. Photo: AFP
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 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".
In Sevastopol, Mr 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," he told a cheering crowd.
Violence in eastern Ukraine
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.
Interior Minister Arsen Avakov said on his official Facebook page that the fighting had killed 20 insurgents and one police officer.
An AFP reporter in the city said its police headquarters were a gutted wreck, with parts of the building on fire as firefighters struggled to douse the blaze.
Mr Putin had flown 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, he 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.