On Saturday, Ukrainian President Volodymyr Zelenskiy called for comprehensive peace talks with Moscow and urged Switzerland to do more to crack down on Russian oligarchs who, he claimed, were using their wealth to wage war on his country.

British intelligence warned that Russia, frustrated by its failure to achieve its objectives since the invasion began on February 24, was now pursuing an attritional strategy that could exacerbate the humanitarian crisis.

Russian forces have suffered heavy losses, and their advance has largely stalled since President Vladimir Putin launched the assault, with long columns of troops bearing down on Kyiv coming to a halt in the suburbs.

But they have laid siege to cities, blasting urban areas to rubble, and in recent days have intensified missile attacks on scattered targets in western Ukraine, away from the main battlefields.

Zelenskiy, who makes frequent impassioned appeals to foreign audiences for help for his country, told an anti-war protest in Bern that Swiss banks were where the “money of the people who unleashed this war” lay and their accounts should be frozen.

Ukrainian cities “are being destroyed on the orders of people who live in European, in beautiful Swiss towns, who enjoy property in your cities. It would really be good to strip them of this privilege,” he said in an audio address.

Neutral Switzerland, which is not a member of the European Union, has fully adopted EU sanctions against Russian individuals and entities, including orders to freeze their wealth in Swiss banks.

The EU measures are part of a wider sanctions effort by Western nations, criticized by China, aimed at squeezing Russia’s economy and starving its war machine.

In an address earlier on Saturday, Zelenskiy urged Moscow to hold peace talks now.

“I want everyone to hear me now, especially in Moscow. The time has come for a meeting, it is time to talk,” he said in a video address. “The time has come to restore territorial integrity and justice for Ukraine. Otherwise, Russia’s losses will be such that it will take you several generations to recover.”

Britain’s Defence Attaché to the United States said British intelligence believes Russia has been taken aback by the Ukrainian resistance to its assault and has so far failed to achieve its original objectives.

“Russia has been forced to change its operational approach and is now pursuing a strategy of attrition” likely to involve the “indiscriminate use of firepower resulting in increased civilian casualties”, Air Vice-Marshal Mick Smeath said in a statement.

Putin, who calls the action a “special operation” aimed at demilitarizing Ukraine and purging it of what he sees as dangerous nationalists, told a rally on Friday in Moscow that all the Kremlin’s aims would be achieved.

On Saturday, Russia said its hypersonic missiles had destroyed a large underground depot for missiles and aircraft ammunition in the western Ivano-Frankivsk region. Hypersonic weapons can travel faster than five times the speed of sound and the Interfax agency said it was the first time Russia had used them in Ukraine.

A spokesperson for the Ukrainian Air Force Command confirmed the attack, but said the Ukrainian side had no information on the type of missiles used.

Even so, the Ukrainian defence ministry, in an update posted on Facebook, said “the operational situation has not changed significantly”. Troops were concentrating their efforts around the strategically important cities of Kyiv, Chernihiv, Kharkiv, Mariupol and Mykolayiv, it said, adding that “Russian troops continue to suffer heavy losses”.