Russia's main attack force in northern Ukraine has been stalled on a highway north of Kyiv since the initial days of the invasion, having failed in what Western countries believe was an initial plan for a lightning assault on the capital.

But images released by private US satellite firm Maxar showed armoured units manoeuvreing in and through towns close to Antonov airport at Hostomel northwest of Kyiv, which has been the site of intense fighting since Russia landed paratroops there in the first hours of the war.

Other elements had repositioned near the small settlement of Lubyanka just to the north, with towed artillery howitzers in firing positions, Maxar said.

"Russia is likely seeking to reset and re-posture its forces for renewed offensive activity in the coming days," Britain's Ministry of Defence said in an intelligence update. "This will probably include operations against the capital Kyiv."

The update said Russian ground forces were still making only limited progress, with logistical issues that had hampered their advance persisting and Ukrainian resistance strong.

Ukraine's general staff also said Russian forces had regrouped after taking heavy losses.

For a seventh straight day, Russia announced plans to cease fire to allow civilians to leave the besieged southeastern port of Mariupol. Ukraine said it would try yet again to mount an evacuation from the city: "We hope it will work today," Deputy Prime Minister Iryna Vereshchuk said.

All previous attempts to reach Mariupol have failed with both sides accusing each other of failing to observe ceasefires, while hundreds of thousands of people are trapped under relentless bombardment without food or water in the most dire humanitarian emergency of the war.

Washington said Russian targeting of civilians in Mariupol was a war crime. Moscow denies it has been targeting civilians in what it calls a "special operation" to disarm and "de-Nazify" Ukraine, and which it says has been going according to plan.

European Union leaders were holding a summit at France's Versailles Palace, expected to be dominated by calls for more action to punish Russia, assist Ukraine and cope with an influx of nearly 2.5 million refugees in just two weeks.

In the two weeks since the invasion, Western countries have swiftly moved to isolate Russia from world trade and the global financial system in ways never before visited on such a large economy.

In the latest move, sources said US President Joe Biden will ask the Group of Seven industrialised countries to strip Russia of normal trade rights, known as "most favoured nation status". That would allow Russian goods to be subjected to new tariffs.

Moscow said on Friday its separatist allies in the southeast had captured the town of Volnovakha north of Mariupol.

The US Senate voted on Thursday to approve legislation providing $US13.6 billion to help Ukraine finance ammunition and other military supplies, as well as humanitarian support.

Russia is the world's leading exporter of combined oil and gas. Its energy exports have largely been exempted from sanctions so far, although Washington has announced it will stop buying Russian crude.

The EU is also working on plans to phase out imports of Russian oil, gas and coal, but Hungarian Prime Minister Viktor Orban said on Friday that the bloc would not put sanctions on Russian energy.

The information war picked up on social media as well, with Russia demanding that Washington stop the "extremist activities" of Facebook owner Meta Platforms, which temporarily lifted a ban on calls for violence against the Russian military and leadership.

The social media company will temporarily allow some posts that call for the death of Putin or Belarusian President Alexander Lukashenko in countries including Russia, Ukraine and Poland, according to internal e-mails to its content moderators.

Australian Associated Press