President Vladimir Putin has marked the fifth anniversary of what Moscow considers the day Crimea became part of Russia by visiting Ukraine's Black Sea peninsula, as NATO, the United States, and the European Union again condemned what they called the "illegal" land grab.

On March 18, 2014, Putin signed a treaty that Moscow claims made Ukraine's Crimea region part of Russia, after Russian forces seized control of the peninsula and organized a referendum that was not recognized by the international community.

Ukraine and the West have slammed Russia's move as an "illegal" annexation, leading to sanctions against Russian individuals and entities.

The annexation of Crimea and Russia's role in the ongoing conflict in eastern Ukraine, where government forces have been fighting against Russia-backed separatists since April 2014, sent ties between Moscow and the West plunging to post-Cold War lows.

The conflict in eastern Ukraine has left around 13,000 people dead, some 30,000 injured, and uprooted well over 1 million Ukrainian citizens, according to UN and Ukrainian officials.

In Washington, Kurt Volker, the U.S. special envoy for Ukraine, called the fifth anniversary of Russia's annexation of Crimea a "sad day."

"This is an illegal occupation, an illegal seizure of territory, and we fundamentally stand behind Ukraine in insisting that its territorial integrity be restored," Volker told journalists.

In a statement, NATO described the annexation of Crimea as "a serious breach of international law and a major challenge to Euro-Atlantic security."

The Western military alliance's North Atlantic Council criticized Russia's "ongoing and wide-ranging military build-up" in Crimea, and raised concerns over its "efforts and stated plans for further military build-up" in the Black Sea region.

The allies also accused the "Russian de facto authorities in illegally annexed Crimea" of carrying out human rights abuses against "Ukrainians, the Crimean Tatars, and members of other local communities," including "extrajudicial killings, abductions, enforced disappearances, violence, arbitrary detentions, arrest, and torture."
A file photo of Reshat Ametov with one of his children. The Crimean Tatar activist's killing in 2014 is still unsolved.
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They said that there would be no return to "business as usual" with Moscow until there was a "a clear, constructive change in Russia's actions."

Meanwhile, Canada has announced a three-year extension of its 200-member military training mission in Ukraine, with Foreign Minister Chrystia Freeland saying that "Ukraine can continue to count on Canada's unwavering support."

"It's very important to send a strong message to Ukraine, to the people of Ukraine, and to the international community that the invasion of Crimea and the annexation of Crimea are a grave breach of international law," the minister added.

Since 2015, nearly 11,000 Ukrainian soldiers have been trained as part of the Canadian mission, which was due to expire at the end of the month.

On the eve of the anniversary, EU foreign-policy chief Federica Mogherini repeated the bloc's "steadfast" commitment to Ukraine's sovereignty and territorial integrity.

The "illegal" takeover of Crimea "remains a direct challenge to international security, with grave implications for the international legal order," Mogherini said in a declaration on behalf of the EU.

Mogherini blamed Moscow for the deteriorating human rights situation in Crimea, saying that residents of the peninsula "face systematic restrictions of fundamental freedoms," while the rights of the Crimean Tatars have been "gravely violated." European Union foreign policy chief Federica Mogherini

Mogherini Slams Russia As EU Marks Fifth Anniversary Of Crimea's 'Illegal Annexation'

The United States, NATO, and the EU also called for the release of 24 Ukrainian sailors being held by Moscow.

In November, Russia captured three Ukrainian ships and their crew members near the Kerch Strait, which links the Black Sea and Sea of Azov.

Russian officials have proclaimed March 18 as the Day of Crimea's Reunification with Russia.

In Crimea, it is a public holiday. Posters celebrating the peninsula's "return to its native land" hung in shop windows and on public transport in the region's main city of Simferopol.

Putin used his visit to Crimea to officially open two new power stations, which he said will fully cover the region's needs after Ukraine cut off energy supplies to the peninsula following its annexation by Moscow.

The power stations in Sevastopol and Simferopol were partially launched last year, but the official inauguration marked the moment they began working at full capacity.

The two power stations were at the center of an international scandal after German conglomerate Siemens said its power turbines had been installed there without its knowledge and in violation of EU sanctions banning the supply of energy technology to Crimea.

The EU widened sanctions against Russian companies and people in 2017 in response to the transfer of the turbines to the Russian-occupied region.

The Russian Foreign Ministry called the decision an "unfriendly and unjustified" step.

In the evening on March 18, Putin appeared on stage at an open-air concert in Simferopol after a meeting with selected representatives of civil society.

The Ukrainian Foreign Ministry protested his visit as a "crude violation of Ukraine's sovereignty and territorial integrity."

Putin's trust and support ratings in opinion polls, which were significantly bolstered by the 2014 annexation of Crimea, have declined in recent months amid Russia's ongoing economic woes.

Putin has dominated politics in Russia for two decades, serving as president or prime minister since 1999.

In 2018, Putin, 66, was reelected to another six-year term.

Critics say he has maintained his near monopoly on power by crushing political opposition and stifling dissent.