TOP HEADLINES

• Residents fleeing the besieged region around the southern port of Mariupol took a convoy of buses and private cars to Ukrainian-controlled Zaporizhzhia. However, a Red Cross convoy couldn't complete its evacuation. 

• Ukraine's troops began to regain control, including around the capital Kyiv and in the southern region of Kherson - the only significant city that Russia had managed to occupy. Russian troops "are continuing their partial retreat" from the north of Kyiv towards the Belarusian border, Ukraine's defense ministry says.

• Russian President Vladimir Putin and Kazakh leader Kassym-Jomart Tokayev concluded during a phone call that it was vital for an agreement to be reached for a neutral, non-aligned, and nuclear-free Ukraine, Kazakhstan's presidential office said.

• The U.S. Defence Department announced $300 million in "security assistance" for Ukraine to bolster its defense capabilities, adding to the $1.6 billion Washington has already committed. 

• Ukrainian helicopters have carried out a strike on a fuel storage facility in Russia's western town of Belgorod, around 40 kilometers (25 miles) from the border, alleged the local governor. 

• A senior Chinese diplomat said that China is not deliberately circumventing sanctions on Russia a day after the European Union warned Beijing against allowing Moscow to work around measures.

• Pope Francis came the closest he has yet to implicitly criticizing Putin, saying a "potentate" was fomenting conflicts for nationalist interests.

• Russia's space director said that restoring normal ties between partners at the International Space Station and other joint space projects would be possible only once Western sanctions against Moscow are lifted.

• A top UN official is set to fly to Moscow Sunday and then to Kyiv to secure a "humanitarian ceasefire" in Ukraine, says the body's chief Antonio Guterres. 

• Russian soldiers were likely exposed to radiation while occupying the area around the Chernobyl nuclear power station over the past four weeks, Ukraine's nuclear agency Energoatom says. 

• The number of Ukrainian fleeing refugees has passed 4.1 million, the United Nations says.

IN DETAIL 

Mariupol, Ukraine 

A Red Cross convoy will try again to evacuate civilians from the besieged port of Mariupol on Saturday as Russian forces looked to be regrouping for new attacks in southeast Ukraine.

Encircled since the early days of Russia's attacks, Mariupol has been Moscow's main target in Ukraine's southeastern region of Donbas. Tens of thousands are trapped there with scant access to food and water.

The International Committee of the Red Cross (ICRC) sent a team on Friday to lead a convoy of about 54 Ukrainian buses and other private vehicles out of the city, but they turned back, saying conditions made it impossible to proceed. 

"They will try again on Saturday to facilitate the safe passage of civilians," the ICRC said in a statement. A previous Red Cross evacuation attempt in early March failed.

An advisor to Ukrainian President Volodymyr Zelenskyy said he was hopeful about the Mariupol evacuations.

"I think that today or maybe tomorrow, we will hear good news regarding the evacuation of the inhabitants of Mariupol," Oleksiy Arestovych told Ukrainian television.

Russia and Ukraine have agreed to humanitarian corridors to facilitate the evacuation of civilians from cities but have often traded blame when the corridors have not been successful.

Seven such corridors were planned for Saturday, Ukraine's Deputy Prime Minister Iryna Vereshchuk said, including one for people evacuating by private transport from Mariupol and by buses for Mariupol residents out of the city of Berdyansk.

After failing to take a major Ukrainian city since it sent troops over the border on February 24, Russia says it has shifted its focus to the southeast, where it has backed separatists since 2014.

In an early morning video address, Zelenskyy said Russian troops had moved toward Donbas and the heavily bombarded northeastern city of Kharkiv.

"I hope there may still be solutions for the situation in Mariupol," Zelenskyy said.

Belgorod, Russia 

Russia accused Ukraine of carrying out an airstrike against a fuel depot in the Russian city of Belgorod on Friday, an incident the Kremlin said could affect peace talks, while a top Kyiv security official denied responsibility.

Russia's defense ministry said two Ukrainian helicopters struck the facility in Belgorod, some 35 kilometers (22 miles) from the border with Ukraine, after entering Russia at an extremely low altitude at around 5 a.m. Moscow time (0200 GMT).

The resulting blaze forced the evacuation of some people, but late in the day, Belgorod mayor Anton Ivanov said fire services were extinguishing the last remnants.

"There is no threat to human life and health. All residents can return to their homes," he said in an online post.

Ukraine's top security official rebuffed the Russian accusation - the first by Moscow of an airstrike on Russian soil since Moscow launched its attacks. Belgorod is one of Russia's leading logistics hubs for the 'special military operation.'

"For some reason, they (Russia) say that we did it, but according to our information, this does not correspond to reality," said Security Council Secretary Oleksiy Danilov.

Earlier, defense ministry spokesman Oleksandr Motuzyanyk said he would neither confirm nor deny a Ukrainian role.

"Ukraine is currently conducting a defensive operation against Russian aggression on the territory of Ukraine, and this does not mean that Ukraine is responsible for every catastrophe on Russia's territory," he said.

Security camera footage from a location verified by Reuters showed a flash of light from what appeared to be a missile fired from a low altitude in the sky, followed by an explosion on the ground.