MARIUPOL, Ukraine — In a triumphant spectacle, President Vladimir Putin today visited the Crimea area and hailed the return it to Russia as the restoration of “historic justice” before a jubilant crowd on the holiday that Russians hold dearest to their hearts.

Yet Putin’s first trip to the Black Sea peninsula since its annexation in March was strongly criticized by both NATO and Ukraine’s Foreign Ministry, which said it trampled on Ukraine’s sovereignty and international law.

Ukraine is struggling with its most serious crisis in decades as pro-Russia insurgents in the east are fighting the central government in Kiev and preparing to hold a referendum Sunday on secession.

Putin’s two Victory Day celebrations, which included a massive show of military muscle in the annual Red Square parade in Moscow and another in the Crimean port of Sevastopol, rubbed salt in the wounds of the interim government in Kiev without ever once mentioning its name.

Victory Day is Russia’s most important secular holiday and a key element of the country’s national identity, honoring the armed forces and the millions who died in World War II.

Tens of thousands flooded the Crimean port of Sevastopol to watch the extravaganza that was the Russian leader’s entrance. Putin boarded a boat to sail past a line of Russian Black Sea Fleet ships anchored in the bay and greeted their crews before watching a flyby of 70 military aircraft.