IN PHOTOS: Putin goes to war in Ukraine

Russian President Vladimir Putin speaks about authorizing a special military operation in Ukraine's Donbass region during a special televised address on Russian state TV, in Moscow, Russia, February 24, 2022, in this still image taken from video. Russian Pool/via Reuters TV

Ukrainian tanks move into the city, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Mariupol, February 24, 2022. Carlos Barria, Reuters

Tanks move into the city, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Mariupol, February 24, 2022. Carlos Barria, Reuters

Cars drive towards the exit of the city after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Kyiv, Ukraine February 24, 2022. Valentyn Ogirenko, Reuters

A Ukrainian rocket launcher vehicle drives west of the coastal city of Mariupol, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Mariupol, February 24, 2022. Carlos Barria, Reuters

A family takes shelter in a metro station in Kyiv early on February 24, 2022. Air raid sirens rang out in downtown Kyiv on Thursday as cities across Ukraine were hit with what Ukrainian officials said were Russian missile strikes and artillery. Daniel Leal, AFP

People take a shelter in a subway station, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Kyiv, Ukraine February 24, 2022. Valentyn Ogirenko, Reuters

UN Secretary-General Antonio Guterres speaks during an interaction with the media after a United Nations Security Council meeting to discuss the ongoing crisis in Ukraine with Russia, in New York City, U.S., February 23, 2022. Carlo Allegri, Reuters

U.S. service members stand on the tarmac of Riga International Airport as they arrive in Latvia, February 24, 2022. Latvian Defence Ministry/Gatis Indrevics handout/Reuters

Militants of the self-proclaimed Donetsk People's Republic are seen next to buses arranged to transport local residents mobilized for military service, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in the separatist-controlled city of Donetsk, Ukraine February 24, 2022. Alexander Ermochenko, Reuters

Smoke is seen coming out of a military installation near the airport, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Mariupol, February 24, 2022. Carlos Barria, Reuters

Black smoke rises from a military airport in Chuguyev near Kharkiv on February 24, 2022. Aris Messinis, AFP

Black smoke rises from a military airport in Chuguyev near Kharkiv on February 24, 2022. Aris Messinis, AFP

Police officers inspect the remains of a missile that fell in the street, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Kyiv, Ukraine February 24, 2022. Valentyn Ogirenko, Reuters

A view shows a building of a military base, which, according to the State Emergency Service of Ukraine, was damaged by fire, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in the town of Brovary, near Kyiv, Ukraine, in this handout picture released February 24, 2022. Press Service of the State Emergency Service of Ukraine/Handout via Reuters

Debris and rubble are seen at the site where a missile landed in the street, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Kyiv, Ukraine February 24, 2022. Valentyn Ogirenko, Reuters

People wait at Kyiv Airport after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, February 24, 2022. Umit Bektas, Reuters

People wait at a bus station to go to western parts of the country, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Kyiv, Ukraine, February 24, 2022. Umit Bektas, Reuters

A sign directing to the Border Control office is seen as people walk at the border crossing between Poland and Ukraine, after Russian President Vladimir Putin authorized a military operation in eastern Ukraine, in Medyka, Poland, February 24, 2022. Kacper Pempel, Reuters

A family arrives at the Polish border crossing after fleeing violence in Ukraine, in Medyka, Poland, February 24, 2022. Bryan Woolston, Reuters

An American woman cries after crossing the border and fleeing the violence in Ukraine, in Medyka, Poland, February 24, 2022. Bryan Woolston, Reuters

And then there is war.

After weeks of back and forth between the powers involved in the conflict in Ukraine, Russian President Vladimir Putin unleashed the guns and declared war.

Putin on Thursday authorized a military operation in eastern Ukraine in what could be the start of war in Europe over Russia's demands for an end to NATO's eastward expansion.

Shortly after Putin spoke, a Reuters witness heard the sound of what appeared to be explosions in the distance from the capital, Kyiv. Gunfire rattled near the capital's main airport, the Interfax news agency said.

Explosions also rocked the breakaway eastern Ukrainian city of Donetsk and civilian aircraft were warned away, as the United States said a major attack by Russia on its neighbor was imminent.

Ukrainian military command centers in the cities of Kyiv and Kharkiv have been attacked by missile strikes, the Ukrainska Pravda news website cited a Ukrainian interior ministry official as saying on Thursday.

Putin said he had authorized a special military operation in breakaway areas of eastern Ukraine to protect civilians in eastern Ukraine, a claim the US had said he would make to justify an invasion.

In a televised address, Putin accused the US and its allies of ignoring Russia’s demand to prevent Ukraine from joining NATO and other guarantees for the security of Russia.

US President Joe Biden described the attack on Ukraine as “unprovoked and unjustified” and said the world will “hold Russia accountable.”

Hours earlier, pro-Russian separatists issued a plea to Moscow for help to stop alleged Ukrainian aggression - claims the United States dismissed as Russian propaganda. - with reports from Reuters