The United Nations is conducting a "safe passage operation" for civilians from the Azovstal steel works in the Ukrainian city of Mariupol, said a spokesman for the UN Office for the Coordination of Humanitarian Affairs on Sunday.
The operation began on April 29th and is being co-ordinated with the International Committee of the Red Cross, Russia and Ukraine, said spokesman Saviano Abreu.
Mr Abreau added that no further details could be released so as not to jeopardise the safety of evacuees and the convoy.
As many as 100,000 people are believed to be blockaded in Mariupol, including up to 1,000 civilians who were hunkered down with an estimated 2,000 Ukrainian fighters beneath the Soviet-era steel plant – the only part of the city not occupied by the Russians.
Mr Abreu called the situation “complex” and would not give further details.
Like other evacuations, success of the mission in Mariupol depended on Russia and its forces in a long series of checkpoints before reaching Ukrainian ones.
People who have fled Russian-occupied areas have at times described their vehicles being fired on. Ukrainian officials have repeatedly accused Russian forces of shelling evacuation routes on which the two sides had agreed.
Russia’s offensive in coastal southern Ukraine and the country’s eastern industrial heartland has meant Ukrainian forces are fighting village by village.
Mariupol, a port city on the Sea of Azov, is a key target because of its strategic location near the Crimea Peninsula, which Russia seized from Ukraine in 2014. Limited evacuations from the city took place on Saturday, but the details had been unclear given the number of parties involved in the negotiations and the volatile situation on the ground.
The Russian defence ministry said 46 people, a group of 25 and another numbering 21, were evacuated from areas near the Azovstal plant.
An Azov Regiment official, the Ukrainian unit defending the steelworks, said on Saturday that 20 women and children were evacuated from the plant itself.
Civilians have sheltered in a maze of underground tunnels while the plant has been under siege.
Western military analysts have suggested that the offensive in the Donbas region, which includes Mariupol, was going much slower than planned. So far, Russian troops and separatists appear to have made only minor gains in the month since Moscow said it would focus its military strength in the east.
In Mariupol, Russia declared victory on April 21st.
Russia's defence ministry said on Sunday it had carried out a missile strike on a military airfield near the port city of Odesa, destroying a runway and a hangar containing weapons and ammunition supplied to Ukraine by the United States and European countries.
On Saturday, Ukraine said Russian missiles had knocked out a newly constructed runway at Odesa’s main airport. It was unclear if they were referring to the same incident and reports could not be immediately verified.
One person was injured in a fire on a Russian defence ministry facility in the southern Belgorod region bordering Ukraine, said Belgorod regional governor on Sunday.
Governor Vyacheslav Gladkov said a local resident suffered minor injuries and his life was not in danger. There were no immediate comments from the defence ministry. Again it was not possible to verify the reports. Russia last month accused Ukraine of a helicopter attack on a fuel depot in Belgorod, for which Kyiv denied responsibility, as well as shelling villages and firing missiles at an ammunition depot.
Other Russian regions that share a border with Ukraine have also reported cross-border shelling incidents.
Meanwhile, US house of representatives speaker Nancy Pelosi pledged continued US support for Ukraine when she met President Volodymyr Zelenskiy in Kyiv.
Pope Francis, in an implicit criticism of Russia, told thousands of people in St Peter’s Square on Sunday Mariupol had been “barbarously bombarded”.
Mr Zelenskiy greeted the US congressional delegation led by Ms Pelosi outside his presidential office the previous day.
“Our delegation travelled to Kyiv to send an unmistakable and resounding message to the entire world: America stands firmly with Ukraine,” said Ms Pelosi, the highest ranking US official to visit Ukraine since Russia invaded on February 24th.
Western nations have imposed broad economic sanctions on Russia and have been shipping increasing quantities of weapons to help Ukraine defend itself. Ms Pelosi said on Friday she hoped to pass a $33 billion (€31 billion) aid package for Ukraine that US president Joe Biden has requested "as soon as possible".
In the east, Moscow is pushing for complete control of the Donbas region, where Russian-backed separatists already controlled parts of Luhansk and Donetsk provinces before the invasion. On Sunday, Kharkiv regional governor Oleh Synehubov warned residents in the north and east of the city to remain in their shelters due to heavy Russian shelling. It was not immediately possible to verify reports of shelling in the area.
Serhiy Gaidai, governor of the Luhansk region, urged people to evacuate while it was still possible. Mr Zelenskiy said in an address on Saturday night that Russia is "gathering additional forces for new attacks against our military in the east of the country".
Russia's defence ministry accused Ukraine's forces of shelling a school, kindergarten and cemetery in villages in the occupied southern Kherson region, said the Russian RIA news agency on Sunday. The ministry said civilians had been killed and wounded but gave no further details. There was no immediate response from Ukraine and the report could not be independently verified. Russian forces captured the town of Kherson, 100km north of Russian-annexed Crimea, in March.
Ukraine's military said in a bulletin that Russian forces were fighting to push north from Kherson to the cities of Mykolayiv and Kryvyi Rih. – AP/Reuters