KYIV, Ukraine - Russian forces suffered heavy losses in a Ukrainian attack that destroyed a pontoon bridge they were using to try to cross a river in the east, Ukrainian and British officials said in another sign of Moscow's struggle to salvage a war gone awry.

Ukraine's airborne command released photos and video of what it said was a damaged Russian pontoon bridge over the Siversky Donets River and several destroyed or damaged Russian military vehicles nearby. The command said its troops 'drowned the Russian occupiers.'

Britain's Defense Ministry said Russia lost 'significant armored maneuver elements' of at least one battalion tactical group in the attack earlier this week. A Russian battalion tactical group consists of about 1,000 troops.

'Conducting river crossings in a contested environment is a highly risky maneuver and speaks to the pressure the Russian commanders are under to make progress in their operations in eastern Ukraine,' the ministry said in its daily intelligence update.

Smoke rises from what appears to be a makeshift bridge across the Siversky Donets River, eastern Ukraine, in this handout image uploaded May 12, 2022. (Ukrainian Airborne Forces Command/via Reuters)

The battle for the Donbas has turned into a village-by-village, back-and-forth slog with no major breakthroughs on either side and little ground gained.

Fierce fighting has been taking place on the Siversky Donets River near the city of Severodonetsk, said Oleh Zhdanov, an independent Ukrainian military analyst. The Ukrainian military has launched counterattacks but has failed to halt Russia's advance, he said.

'The fate of a large portion of the Ukrainian army is being decided - there are about 40,000 Ukrainian soldiers,' he said.

Firing on residential areas

The Ukrainian military chief for the Luhansk region of the Donbas said 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.

In the south, Ukrainian officials claimed another success in the Black Sea, saying their forces took out a Russian logistics ship that was trying to deliver an anti-aircraft system. There was no confirmation from Russia, and no casualties were reported.

FILE - A child and her family who fled from Mariupol arrive at a reception center for displaced people in Zaporizhzhia, Ukraine, May 8, 2022.

In the ruined southern port of Mariupol, Ukrainian fighters holed up in a steel plant faced continued Russian attacks on the last stronghold of resistance in the city. Sviatoslav Palamar, deputy commander of Ukraine's Azov Regiment, said his troops will hold out 'as long as they can' despite shortages of ammunition, food, water and medicine.

Justin Crump, a former British tank commander who is now a security consultant, said Moscow's losses have forced it to downsize its objectives in Ukraine. He said the Russians have had to use hastily patched-together units that haven't trained together.

Ukraine Russia Mariupol

'This is not going to be quick. So we're settled in for a summer of fighting at least. I think the Russian side is very clear that this is going to take a long time,' he said.

For its part, Ukraine is asking for more arms to fend off the invasion, and the European Union's foreign affairs chief announced plans to give Kyiv an additional 500 million euros ($520 million) to buy heavy weapons.

Ukrainian Defense Minister Oleksii Reznikov welcomed the heavy weapons making their way to the front lines but admitted there is no quick end to the war in sight.

'We are entering a new, long-term phase of the war,' he wrote in a Facebook post. 'Extremely difficult weeks await us. How many there will be? No one can say for sure.'