The head of the International Atomic Energy Agency has arrived in Ukraine to deliver technical assistance ensuring the safety and security of Ukraine’s nuclear facilities. 

As part of the trip, IAEA Director General Rafael Mariano Grossi will be visiting one of Ukraine’s nuclear power plants this week, the agency said.

Grossi's visit comes after Ukraine requested assistance in ensuring safety and security at its nuclear plants in the midst of Russia's invasion. 

“We must act now to help prevent the danger of a nuclear accident,” said Grossi in a Twitter post.

"Ukraine has one of Europe’s largest nuclear power programs," he said in a separate statement. "The IAEA’s presence, where needed to ensure safety and security, is of paramount importance. We are ready to provide the necessary support now."

A Russian strike hit the regional government building in the southern Ukrainian city of Mykolaiv, the regional governor, ​​Vitaliy Kim, said on Telegram on Tuesday. 

The southern port city has been under attack for weeks. The governor said the regional administration building was hit, adding that his personal office was destroyed too. 

Kim said most people appeared to have survived the incident. 

The State Emergency Service of Ukraine said at least 3 people had died in the attack. NBC News was not able to verify the death toll. 

Kim said at least eight civilians and three military personnel were still trapped under the rubble. It was not immediately clear how many people were injured. 

Firefighters tackle a blaze in Lutsk, western Ukraine, after Russian attacks struck a fuel storage facility on Tuesday.

Ukraine's foreign minister has called on states to criminalize the use of the "Z" symbol, which has been used as a way to publicly show support for Russia's invasion. 

“’Z’ means Russian war crimes, bombed out cities, thousands of murdered Ukrainians. Public support of this barbarism must be forbidden,” Ukrainian Foreign Minister Dmytro Kuleba said in a tweet Tuesday.

The original meaning of the “Z” symbol has remained something of a mystery since it was first spotted on Russian tanks.

In the weeks since, the letter ”Z” has become a symbol used to show support for Russia's invasion of Ukraine. Two German states have already banned the portrayal of the symbol.

Kremlin spokesman Dmitri Peskov has said that Russia would only consider using nuclear weapons if there was a threat to the "existence of the state in our country." 

However, he said that "any outcome" of Russia's invasion of Ukraine would not be a "reason for usage of a nuclear weapon." Peskov made the comments during an interview with PBS on Monday. 

He said that Moscow has a "security concept that very clearly states that only when there is a threat for existence of the state, in our country, we can use and we will actually use nuclear weapons to eliminate the threat for the existence of our country."

Pressed to clarify more on Russia's position on the use of nuclear weapons, he said: "No one is thinking about using ... even about the idea of using a nuclear weapon." 

Three humanitarian corridors have been agreed to open on Tuesday, Deputy Prime Minister Iryna Vereshchuk said in a Telegram post.

The decision came a day after Ukrainian President Volodymyr Zelenskyy said in a video address Monday that "the Russian army did not let us organize a single humanitarian corridor today, did not provide cease-fire."

The corridors will open at the Donetsk and Zaporizhzhia regions, allowing citizens to go from Mariupol to Zaporizhzhia using individual vehicles. Thirty buses have already left Zaporizhzhia to evacuate Mariupol residents from Berdyansk.

Civilians will also be able to travel from Melitopol to Zaporizhzhia and from the city of Enerhodar to Zaporizhzhia by private transport.

Russian and Ukrainian negotiators are meeting in Istanbul for the latest round of peace talks Tuesday morning.

In the below photo, Turkish President Tayyip Erdogan addresses Russian and Ukrainian negotiators before their face-to-face talks in Istanbul on Tuesday.

Japan will ban the export of luxury goods to Russia from April 5, the country's Ministry of Economy, Trade and Industry said in a statement on Thursday.

The ban comes as the latest effort to pressure Russia to end its invasion of Ukraine. The banned goods include luxury cars, laptop, jewelry, alcohol and tobacco.

The ban is based on a revised Foreign Exchange and Foreign Trade Law. Before the revision, Japan had banned the export of weapons, carbon fiber and semiconductors to Russia.

Ukrainian forces have seen "some success" conducting "localized" counter attacks north west of Kyiv as Russian forces elsewhere attempt to "reorganize and reset their forces," Britain's defense ministry has said.

In its daily intelligence update Tuesday, the British defense ministry said Russian forces had been pushed back from a number of positions north west of Kyiv. However, it said Russian forces still poses a significant threat to the capital through their strike capability.

Russian forces have maintained their offensive on the besieged port city of Mariupol, with continued heavy shelling of the city, it said. However, it noted that the center of the city remains under Ukrainian control. 

It said that in other regions, Russian troops were maintaining blocking positions while attempting to reset their forces.