Russian invasion of Ukraine: Key developments this week as Putin's troops appear to withdraw from Kyiv

Here is a summary of the main events of this week, as the war between Russia and Ukraine continues.

Russia demands gas payments be made in roubles

Gas used for heating and electricity was still flowing from Russia to Europe on Friday.

However, the Kremlin has threatened to stop sending gas to "unfriendly" countries - including all those in Europe - unless they pay in roubles.

Germany and some others have ruled out rouble payments, leading to the prospect of pipes being cut off.

While the UK only gets a small amount of its gas from Russia, prices are expected to rise here, as British energy suppliers compete with other European companies to buy UK gas.

Russian forces retreat from Kyiv

Towards the end of the week, Vladimir Putin's troops retreated from Kyiv and the Northern city of Chernihiv.

A man walks in a destroyed street of the eastern Ukraine city of Kharkiv on Saturday, as Ukraine said today Russian forces were making a "rapid retreat" from northern areas around the capital Kyiv and the city of Chernigiv. (Photo by FADEL SENNA/AFP via Getty Images)

Ukrainian fighters reclaimed several areas near the capital after forcing the Russians out or moving in after them.

Admiral Sir Tony Radakin, the head of Britain's armed forces, said that Russia's bid to take all of Ukraine during its invasion looks to have "fallen apart".

He announced the UK was "incredibly cautious" about believing Russian claims of withdrawing from Kyiv, but said there did appear to be signs the Kremlin was preparing to focus its efforts on the east and south of Ukraine.

However, Ukranian President Volodymyr Zelensky has warned that retreating Russian forces are creating a "catastrophic" situation for civilians in Kyiv by leaving mines around homes, abandoned equipment and "even the bodies of those killed".

The Red Cross hoped to lead an evacuation of thousands of civilians from Mariupol, but were unable to go ahead as planned. (Photo by EMRE CAYLAK/AFP via Getty Images)

Russian troops give up Chernobyl

Russian troops left the heavily contaminated Chernobyl nuclear site early on Friday after returning control to the Ukrainians.

Ukraine's state power company, Energoatom, said the pull-out at Chernobyl came after soldiers received "significant doses" of radiation from digging trenches in the forest in the exclusion zone around the closed plant, although there was no independent confirmation of that.

The exchange of control at Chernobyl happened amid growing indications the Kremlin is using talk of de-escalation in Ukraine as cover to regroup, resupply its forces and redeploy them for a stepped-up offensive in the eastern part of the country.

Evacuation team fails to reach Mariupol

A Red Cross team intending to help people leave the besieged city of Mariupol was unable to reach the port city as planned on Thursday.

The crew of nine from the International Committee of the Red Cross (ICRC) were forced to turn back after "arrangements and conditions made it impossible to proceed".

The Red Cross said in a statement that the team hoped to try again on Saturday.

Sean Penn urges billionaires to buy aircraft for Ukraine

The Hollywood actor has called on anyone with $300m to spare to buy two squadrons of F-15 or F-16 aircraft for Ukraine, to help them fight back against Russia’s invasion.

He urged private sector buyers for their help on Twitter, writing: “One billionaire could end this war in Ukraine.”

Mr Penn was in Kyiv on the day war broke, as he had been filming a documentary about the ongoing conflict between Russia and Ukraine.

The US government has so far refused to supply the Ukrainian Airforce with fighter jets, due to concern that this action would be seen as escalation by a nuclear-armed Russia.

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