Ukrainian President Volodymyr Zelensky has said he discussed Russian attacks on the Ukrainian energy system in a "positive and productive" call with US President Donald Trump.
"We discussed opportunities to bolster our air defense, as well as concrete agreements that we are working on to ensure this. There are good options and solid ideas on how to truly strengthen us," Mr Zelensky wrote on X.
Earlier, Ukrainian drones struck Russia's Bashneft oil refinery in Ufa, causing explosions and a fire, a source in Ukraine's SBU security service said.
"This is the third SBU deep strike in Bashkortostan in the last month - 1,400 kilometers from Ukraine. Such strikes demonstrate that there are no safe places in the deep rear of the Russian Federation," the source said.
It comes as US First Lady Melania Trump said she had secured the release of Ukrainian children abducted by Russia after establishing an extraordinary back channel of communication with President Vladimir Putin.
In a rare public announcement at the White House, she revealed weeks of behind the scenes diplomacy with the Kremlin chief after he held a summit in Alaska with her husband, US President Donald Trump.
Eight children displaced by Moscow's 2022 invasion of Ukraine had been returned to their homes in the last 24 hours, she said.
The 55-year-old said that Mr Putin had agreed to help after she passed him a letter through Trump at the summit, a meeting which otherwise ended without a breakthrough in resolving the war now in its fourth year.
"Much has unfolded since President Putin received my letter last August. He responded in writing signalling a willingness to engage with me directly and outlining details regarding the Ukrainian children residing in Russia," she told reporters.
"Since then, President Putin and I have had an open channel of communication regarding the welfare of these children."
The Slovenian-born former model said that both sides had also had "several back channel meetings and calls, all in good faith".
"My representative has been working directly with President Putin's team to ensure the safe reunification of children with their families between Russia and Ukraine," she said.
"In fact, eight children have been rejoined with their families during the past 24 hours."
Seven of them were returned to Ukraine from Russia, she said, while one young girl went back to Russia from Ukraine.
Three were separated from their parents and "displaced to the Russian Federation by frontline fighting," she said.
The others including the girl returned to Russia were "separated from family members across borders" by the conflict.
Kyiv has accused Moscow of abducting almost 20,000 children from parts of the east and south of Ukraine after Moscow's troops invaded in February 2022.
Ukraine has made the issue of the abducted children a diplomatic priority.
The International Criminal Court has issued an arrest warrant for Mr Putin and his children's rights commissioner, Maria Lvova-Belova, over the allegations of child abductions.
Russia has said it moved some Ukrainian children from their houses or orphanages for protection due to the threat of hostilities.
Melania Trump said in her announcement that Russia had "demonstrated a willingness" to share details to identify abducted children, including biographies and photos.
She said she would continue to work for more children to return to their homes.
"This is an important initiative for me. It is built on shared purpose and lasting impact," she added.
The announcement marked a rare glimmer of progress in the Ukraine war, which President Trump vowed to solve within 24 hours of taking office but now admits is the most difficult conflict he has tried to solve.
It was also a rare solo appearance by Melania Trump, who has been an elusive figure at the White House since her husband's return to power in January, preferring to spend her time in New York or Florida.
But she has highlighted a number of initiatives, often involving children.
Ms Trump also accompanied her husband on his state visit to Britain in September, making a joint appearance with Princess Catherine, wife of heir to the throne Prince William.
Twenty-three children rescued from Russian-occupied Ukraine, senior official says
Meanwhile, President Volodymyr Zelenskiy's chief of staff has said that 23 Ukrainian children and adolescents have been brought out of Russian-occupied areas of the country to territory under Kyiv's control.
Andriy Yermak, writing on the Telegram messaging app, said the rescue was carried out under the president's "Bring Kids Back UA" programme aimed at bringing to safe areas children deported to Russia or confined to Russian-occupied areas of Ukraine.
Yermak said those returning included two sisters who refuseda demand to attend Russian schools made by Russia-installedauthorities who had threatened to remove the girls from their mother's care.
Another teenage boy similarly refused to attend Russianschool and one child and her mother were refused permission toleave occupied areas as one of their relatives was serving inthe Ukrainian military.
Ukraine says Russia has illegally deported or forcibly displaced more than 19,500 children to Russia and Belarus inviolation of the Geneva Conventions.
Research by Yale's School of Public Health suggested in September that the number could be closer to 35,000.
Russia denies it has deported children from Ukraine, saying it has taken action to ensure they are safe from wartime hostilities.
