Russia lost significant numbers of troops and important equipment when Ukrainian forces thwarted their attempt to cross a river in the east, British officials have said.
It is another sign of Moscow’s struggle to win decisive victories and salvage a war gone awry.
Ukrainian authorities, meanwhile, opened the first war crimes trial of the conflict, in proceedings that will be closely watched by international observers eager to ensure atrocities are fairly prosecuted.
A Russian soldier stands accused of killing a Ukrainian civilian in the early days of the war.
The trial gets underway as Russia’s campaign in Ukraine’s eastern industrial heartland of the Donbas makes faltering progress.
Ukrainian news reports said troops thwarted Russian passage across the river earlier this week, leaving dozens of tanks or military vehicles damaged or forcing troops to abandon them.
Britain’s Ministry of Defence (MoD) said on Friday that Russia lost “significant” elements of at least one battalion tactical group — about 1,000 troops — as well as equipment used to quickly deploy a makeshift floating bridge while trying to cross the river.
“Conducting river crossings in a contested environment is a highly risky manoeuvre and speaks to the pressure the Russian commanders are under to make progress in their operations in eastern Ukraine,” the MoD said in its daily intelligence update.
They have struggled to do so even after diverting troops from other parts of the country to the Donbas, the statement said.
Some analysts initially thought the campaign in the Donbas might offer Russian President Vladimir Putin an easier battleground, after his forces failed to overrun the capital Kyiv.
In that grinding fighting, the Ukrainian military chief for the eastern Luhansk region said on Friday that Russian forces opened fire 31 times on residential areas the day before, destroying dozens of homes, notably in Hirske and Popasnianska villages, and a bridge in Rubizhne.
Meanwhile, Ukrainian officials claimed another success in the Black Sea, saying their forces took out another Russian ship, though there was no confirmation from Russia and no casualties were reported.
The Vsevolod Bobrov logistics ship was badly damaged but not thought to have sunk when it was hit while trying to deliver an anti-aircraft system to Snake Island, said Oleksiy Arestovych, an adviser to the Ukrainian president Volodymyr Zelensky.
In April, the Ukrainian military sank the Moskva cruiser, the flagship of Russia’s Black Sea fleet.
In March, it destroyed the landing ship Saratov.
On Thursday, Finland’s president and prime minister announced that the Nordic country should apply right away for membership in the military defence pact founded in part to counter the Soviet Union.
Finland’s Parliament still has to weigh in but the announcement means it is all but certain to apply — and gain admission.
Sweden, likewise, is considering putting itself under Nato’s protection.
The Kremlin warned it may take retaliatory “military-technical” steps.
The support of Nato countries to Ukraine has been key in its surprising success in stymieing Russia’s invasion.
Western nations have also imposed tough sanctions on Russia to punish it for the war — and outrage only grew after allegations of atrocities committed by Moscow’s troops began to emerge.
On February 28, four days after Russia invaded Ukraine, Sgt Vadim Shyshimarin, 21, was among a group of Russian troops that had been defeated by Ukrainian forces, according to the prosecutor general.
As the Russians fled, they headed to a village in the Sumy region, and Shyshimarin is accused of shooting a 62-year-old Ukrainian man in the head there.
The killing is just one of several thousand potential war crimes that Ukrainian prosecutors are investigating.
Many of the alleged atrocities came to light last month after Moscow’s forces ended their bid to capture Kyiv and withdrew, exposing mass graves and streets strewn with bodies in towns such as Bucha.
In a small Kyiv courtroom on Friday, scores of journalists, many with cameras, packed together to see the start of the proceedings.
Shyshimarin was asked a series of questions, including whether he understood his rights and whether he wanted a jury trial.
He declined the latter.
His lawyer Victor Ovsyanikov acknowledged that the case against him is strong, but said the final decision over what evidence will be allowed will be made by the court.
He did not indicate what defence he will offer.
Shyshimarin, a member of a tank unit captured by Ukrainian forces, admitted that he shot the civilian in a video posted by the Security Service of Ukraine, saying he was ordered to do so.
In Kharkiv, Ukraine’s second-largest city, classes are being taught in a subway station used as a bomb shelter that has become home for many families.
“It helps to support them mentally. Because now there is a war, and many lost their homes … some people’s parents are fighting now,” said teacher Valeriy Leiko.
In part thanks to the lessons, he said, “they feel that someone loves them”.
An older student, Anna Fedoryaka, monitored lectures on Ukrainian literature being given by Kharkiv professor Mykhailo Spodarets online from his basement.
The internet connection was a problem for some, Ms Fedoryaka said.
And, “it is hard to concentrate when you have to do your homework with explosions by your window”.