The European Union will likely agree an embargo on Russian oil imports "within days", according to its biggest member Germany, as Moscow said it saw its economic ties growing with China after being isolated by the West over its invasion of Ukraine.

Ukrainian President Volodymyr Zelenskiy told global business leaders in Davos on Monday that the world must increase sanctions against Russia to deter other countries from using "brute force" to achieve their aims.

Many of the EU's 27 member states are heavily reliant on Russian energy, prompting criticism from Kyiv that the bloc has not moved quickly enough to halt supplies.

Hungary stuck to its demands for energy investment before it agrees to such an embargo, clashing with EU states pushing for swift approval. The EU has offered up to 2 billion euros ($2.14 billion) to central and eastern nations lacking non-Russian supply.

"We will reach a breakthrough within days," Germany's economy minister, Robert Habeck, told broadcaster ZDF.

The European Commission and United States were working in parallel on a proposal to cap global oil prices, he said.

"It is obviously an unusual measure, but these are unusual times," he said.

Russia's three-month long invasion, the biggest attack on a European state since 1945, has seen over 6.5 million people flee abroad, turned entire cities into rubble, and prompted the unprecedented imposition of Western sanctions on Russia.

In a further symbolic indication of Russia's isolation, U.S. coffee chain Starbucks became the latest Western brand to say it was pulling out of the country on Monday.

Foreign Minister Sergei Lavrov said the Kremlin would focus on developing ties with China as economic links with the United States and Europe were cut.

"If they (the West) want to offer something in terms of resuming relations, then we will seriously consider whether we will need it or not," he said in a speech, according to a transcript on the foreign ministry's website.

"Now that the West has taken a 'dictator's position', our economic ties with China will grow even faster."

The comments came as U.S. President Joe Biden toured Asia, where he said he would be willing to use force to defend Taiwan against Chinese aggression - a comment that seemed to stretch the limits of the ambiguous U.S. policy towards the self-ruled island.

DONBAS FIGHTING

Russia sent thousands of troops into Ukraine on Feb. 24 for what it calls a "special operation" to demilitarise its neighbour and root out dangerous nationalists - claims dismissed by Kyiv and Western countries as false pretexts for a land grab.

Having captured the port city of Mariupol in southeastern Ukraine last week after a months-long siege, Russian forces now control a largely unbroken swathe of the east and south.

They are trying to encircle Ukrainian forces and fully capture the Luhansk and Donetsk provinces that make up the eastern Donbas region, where Moscow backs separatist forces.

A total of 12,500 Russians were trying to seize Luhansk, the region's governor, Serhiy Gaidai, said on Telegram. The town of Sievierodonetsk is being destroyed, but Ukraine has forced Russian troops out of Toshkivka to its south, Gaidai added.

Donetsk regional governor Pavlo Kyrylenko told local television that shelling was occurring along the front line, with the coal mining town of Avdiivka being hit round the clock.

Russian forces fired on 38 communities in Donetsk and Luhansk on Monday, killing seven and injuring six, Ukraine's Joint Forces Task Force military command said in its nightly update.

Reuters was not immediately able to verify the information.

Zelenskiy revealed Ukraine's worst military losses from a single attack of the war on Monday, saying 87 people had been killed last week when Russian forces struck a barracks at a training base in the north.

"Each time we tell our partners that we need modern anti-ballistic weapons, modern military aircraft, we are not making just empty requests," he said late on Monday.

"These requests are the lives of many people who would not have been killed if we had received all the weapons we have been requesting."

A pledge by Denmark to send Harpoon anti-ship missiles and a launcher to Ukraine, announced by the United States on Monday, is the first sign since the Russian invasion that Kyiv will receive U.S.-made weapons that significantly extend its striking range.

The Harpoons, made by Boeing, could be used to push the Russian navy away from Ukraine's Black Sea ports, allowing exports of grain and other agricultural products to resume.

In the first of what could be many war crimes trials arising from the invasion, a court in Kyiv sentenced a young Russian tank commander to life in prison for killing an unarmed civilian.

Ukraine is investigating over 13,000 alleged Russian war crimes, according to the website of its prosecutor general.

Russia has denied targeting civilians or involvement in war crimes.

Ukraine has been trying to secure a prisoner swap for the fighters who surrendered in Mariupol. A Russian deputy foreign minister was quoted as saying Moscow could discuss a swap.

At a cemetry outside Mariupol, treading through long rows of fresh graves and makeshift wooden crosses, Natalya Voloshina, who lost her 28-year-old son in the fight for the city, said many of Mariupol's dead had no one left to honour their memory.

"Who will bury them? Who will put up a plaque?" she asked.

"They have no family."

Reuters