Ukraine's SBU security service said on Friday it had detained a special operations forces unit commander accused of disclosing plans of operations behind enemy lines to Russia's GRU military intelligence.

"The aggressor was most interested in intelligence on sabotage and reconnaissance raids by Ukrainian special forces behind the front line in the Zaporizhzhia, Kherson and Crimean directions," SBU said via the Telegram messaging app.

The "mole", whose rank corresponded to lieutenant colonel, reportedly had access to information on planned routes, weapons and targets.

Russian forces planned to use the intelligence to eliminate special forces soldiers on the front line and in the Russian-occupied parts of southern Ukraine, the statement said.

SBU said Russia's military intelligence "activated" the unit commander in the spring of this year but that he was recruited before Moscow's full-scale invasion in February 2022 through his acquaintances in Russia.

The security service said that Ukraine's top military leadership aided with the case and the suspect could face life in prison on treason charges.

One killed in Odesa air attack, Zelenskyy says

A Russian air attack struck a residential building and energy installations on Thursday evening in and near Ukraine's Black Sea port of Odesa, knocking out a boiler plant used for heating, officials said.

Odesa Regional Governor Oleh Kiper said on Telegram that the strike destroyed a multi-storey residential building in the port city's centre, damaged high-rise apartments and 30 cars, and set fire to other apartments.

"Enemy fire also damaged the main central heating pipeline. The boiler plant has been temporarily shut down and repair work is under way," he said.

Odesa's mayor Hennadiy Trukhanov said the attack temporarily left over 40,000 people without heating. Heating infrastructure for one of the city's maternity hospitals was also damaged, he said.

Engineers finished the repairs by the morning and heating would resume for impacted consumers within the next few hours, Mr Trukhanov added.

Ukrainian President Volodymyr Zelenskyy said the strike killed one person and injured 10.

"Last night there was a combined massive attack on Odesa. Missiles and drones were used … The territory of port was also hit," Mr Zelenskyy said in a message on social media on Friday.

Ukraine's air force said that it shot down 25 out of 29 drones and one of two Kh-59/69 guided missiles launched by Russia during an overnight attack.

Meanwhile, the RIA state news agency reported on Friday that Russian forces had captured the village of Stepanivka in Ukraine's eastern Donetsk region.

Ukrainian Defence Minister Rustem Umerov told a press conference in Norway that Ukraine is fighting to liberate all territory captured by Russia in the last decade, and is not shifting its focus in the war.

Mass displacement looms as Russia targets Ukraine's energy sector, UN warns

Any additional Russian attacks on Ukraine's energy system could trigger a further wave of mass displacement as winter approaches, a senior UN official said on Friday.

As the war grinds towards its third winter, civilians are more vulnerable than at any other winter during the conflict due to Russian strikes on its energy system and donor fatigue, UN Humanitarian Coordinator in Ukraine Matthias Schmale said.

"The real concern is if they were to target the energy sector again, this could be a tipping point … for further mass movements, both inside the country and outside the country," he told reporters in Geneva.

Any further displacement would add to the 3.6 million that are currently displaced within Ukraine and the more than six million who have fled across its borders to escape the conflict that began when Russia invaded in February 2022.

Around 65 per cent of Ukraine's own energy production is currently offline due to Russian strikes which is more than at this same point of the year in 2022 or 2023, Mr Schmale said.

The United Nations and partners are implementing the Humanitarian Winter Response Plan aiming to address emergency needs by delivering fuel and other items to help people stay warm.

He said shelters known as Invincibility Points, where residents can warm up and drink tea, have also been set up.

Mr Schmale voiced particular concern about people stranded in high-rise buildings and people with disabilities living close to the front line in Kharkiv and Kherson.

So far, aid workers have reached about half of the 1.7 million people targeted but funding shortages are constraining efforts, he said.

This year, the UN humanitarian response has received $US1.8 billion  ($2.7 billion) out of US$3.1 billion  ($2.8 billion) sought, which is less than in 2022 and 2023, he said.

"So the trend is clearly downwards, but we still get a lot of money compared to other crisis situations and our plea is that this is maintained because the war is not over."

UK jets track Russian aircraft near British airspace

British jets tracked a Russian aircraft flying close to the country's airspace, the Royal Air Force said on Friday, days after the Royal Navy also detected Russian military ships passing through the English Channel.

"Our adversaries should be in no doubt of our steadfast determination and formidable ability to protect the UK," Luke Pollard, British minister for the armed forces, said in a statement.

The Royal Navy and RAF routinely track the movements of Russian warships and jets near its waters and airspace.

The Ministry of Defence (MOD) said it was the second time in three months the RAF and the Royal Navy had spotted Russian aircraft and ships within a week of each other.

Two RAF Typhoons monitored a Russian Bear-F bomber aircraft flying over the North Sea on Thursday, the MOD said.

The Royal Navy shadowed two separate groups of Russian military vessels, totalling five ships, which were headed towards the Atlantic and Baltic, it said.

Reuters