Russian President Vladimir Putin visited a captured Ukrainian city on Sunday for the first time since invading the country last year.

Putin made an unannounced trip to the coastal city of Mariupol, a city Russian forces reduced to near ruins with artillery fire earlier in the invasion. Footage shows Putin driving around the city at night while Russia's Deputy Prime Minister Marat Khusnullin explains the efforts Russian forces are taking to rebuild the city.

Russian President Vladimir Putin has paid a surprise visit to Mariupol, a Ukrainian port captured by Russia after its forces pounded much of it to ruins.

An official video shows Mr Putin driving a car through streets at night and speaking to people. The Kremlin says it happened late on Saturday.

It is believed to be his first trip to a newly-occupied Ukrainian territory.

Mariupol's exiled mayor told BBC News that Mr Putin was a "criminal" who had "returned to the scene of the crime".

Russian President Vladimir Putin visited the occupied port city of Mariupol, his first trip to Ukrainian territory that Moscow illegally annexed in September and a show of defiance after the International Criminal Court issued a warrant for his arrest on war crimes charges.

The human rights organization Amnesty International says Russia committed a war crime by bombing a theater where hundreds of civilians were sheltering during the March siege of Mariupol, the southern Ukrainian port city that Russian troops destroyed and now occupy.

The strike killed at least a dozen people. Russia blocked Amnesty's Crisis Response Team from entering Mariupol so researchers interviewed survivors in other parts of Ukraine, examined satellite data and hired a physicist to model the detonation.

Ukrainian fighters have ended their weeks-long defense of a besieged steel plant in the strategic port city of Mariupol, as hundreds of combatants — dozens of them seriously wounded — were evacuated from the complex Monday.

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Civilians trapped in the grim battle for control of the Ukrainian port city of Mariupol have been allowed to start leaving the city by besieging Russian forces, the United Nations and the Ukrainian government said Sunday.

Invading Russian troops have been trying to oust a stubborn detachment of Ukrainian troops at a vast steel mill complex on the edge of the city, with about a thousand Ukrainian civilians also trapped at the site.

Previous efforts to establish a “humanitarian corridor” to bus out the civilians have repeatedly broken down.

Ukrainian authorities are planning to evacuate more civilians from Mariupol on Monday, after dozens were finally brought to safety following weeks trapped under heavy fire in the strategic port city’s Azovstal steel complex.

The civilians had been sheltering in bunkers beneath the steelworks that is the last redoubt for Ukrainian forces in Mariupol.

On Sunday, Ukrainian president Volodymyr Zelenskiy said about 100 civilians evacuated from the steel works and would arrive in the Ukrainian-controlled city of Zaporizhzhia on Monday morning.

Russian forces shelled the Azovstal steel plant soon after some civilians were evacuated from the besieged facility, Ukrainian military officials said ahead of fresh evacuations planned for Ukraine's final stronghold in Mariupol on Monday.

The United Nations and the International Committee of the Red Cross began evacuating civilians from the besieged southern port city of Mariupol, and the operation will continue on Monday.

“The Mariupol humanitarian operation will continue until we achieve our goals — saving the lives of our citizens,” Iryna Vereshyuk, Ukraine’s deputy prime minster, said in a message she posted on Telegram, according to an NBC News translation. Around 100 civilians have been rescued so far, Ukrainian President Volodymyr Zelenskyy said.

Defenders of the besieged city of Mariupol will fight to the end against Russian forces, Ukrainian Prime Minister Denys Shmyhal says.

The port city has not fallen despite an ultimatum from Moscow to remaining fighters to give up, he said.

Ukraine's Foreign Minister Dmytro Kuleba said Russia has chosen to raze Mariupol to the ground.

Local officials said Russian forces have announced they will stop anyone from entering or leaving the city.