Ukraine's security service says it has arrested the country's most senior pro-Russian politician, Viktor Medvedchuk. The opposition party leader had been under house arrest suspected of treason but fled shortly after the Russian invasion.

President Zelensky offered Russia to trade him for captured Ukrainians. Earlier on Tuesday, he said that new mass graves are being discovered in formerly occupied areas "almost daily".

Russia and Ukraine are building up forces in the eastern region of Donbas. Satellite images show Russian troops and equipment in at least three places on Ukraine's border.

Meanwhile in Donbas there are signs that Ukraine is bringing in more military equipment, although on a smaller scale.

The US says it cannot confirm unverified information that Russia has used chemical weapons in its siege of Mariupol.

In Russia

President Putin has made a rare public appearance alongside the leader of Belarus, Alexander Lukashenko. He said peace talks had reached a dead end after Ukraine made "fake claims" about war crimes.

Putin described Russia's military goals in Ukraine as noble. He said Russia would continue its "special operation" to defend Russian speakers in eastern Ukraine.

Lukashenko said allegations of atrocities in northern Ukraine were "a psychological operation carried out by the English".

The two leaders vowed to "deepen integration" between their countries.

Diplomacy

US President Joe Biden and UK Prime Minister Boris Johnson have spoken by phone, discussing how to increase economic pressure on Russia and end Western reliance on its oil and gas.

The call came hours before Biden charged that Putin was a "dictator" carrying out a genocide in Ukraine. His speech marked the first time Biden or a member of his team referred to Russian actions as "genocide," earlier only going so far as to describe them as war crimes.

A multi-confessional delegation of religious leaders is visiting the western Ukrainian city of Chernivtsy, on a mission to provide comfort to victims of the war.

Ukrainian President Volodymyr Zelensky has said in a speech to the Lithuanian parliament that the European Union was still too hesitant in imposing sanctions on Moscow.

He also called for all governments to boycott Russian oil, saying that failing to do so would allow Russia to continue to seek a military solution to the conflict with Ukraine.

This is Jude Sheerin in Washington DC and Max Matza in Seattle signing off and handing over to our colleagues, Ayeshea Perera in Singapore and Andrew Clarance in Delhi.

BBC