MOSCOW, June 18 (Reuters) - Russia reported fierce fighting on Sunday on three sections of the front line in Ukraine while Ukraine's president praised his troops for repelling enemy advances and said their counter-offensive was progressing well.

The assesments of action along the 1,000-km (600-mile) long front were made a day after an African peace mission wrapped up talks with Russian President Vladimir Putin. The mission failed to spark enthusiasm from either Moscow or Kyiv.

The United Nations, meanwhile, accused Moscow of failing to allow it to provide assistance to Russian-controlled areas of Ukraine affected by the breach of a big power dam that flooded vast areas of land and left thousands homeless.

A Russian-installed official said Ukraine had recaptured Piatykhatky, a village in the southern Zaporizhzhia region, and were entrenching themselves there while coming under fire from Russian artillery.

"The enemy's 'wave-like' offensives yielded results, despite enormous losses," the official, Vladimir Rogov, said on the Telegram messaging app.

Russia's defence ministry made no mention of Piatykhatky in its daily update, in which it said its forces had repelled Ukrainian attacks in three sections of the front line. Russia's Vostok group of forces said Ukraine had failed to take the settlement.

The evening report by the general staff of Ukraine's armed forces also made no mention of Piatykhatky. Last week, Ukraine said it had recaptured a nearby settlement, Lobkove, and villages further east, in the Donetsk region, at the start of its counteroffensive.

Ukrainian President Volodymyr Zelenskiy praised his troops for being "very effective in repelling assaults" near Avdiivka, one of the hot spots in the fighting in eastern Ukraine.

The long-anticipated Ukrainian counter-offensive was proceeding well, he said in his nightly video address.

"Our troops are on the move: position by position, step by step, we are going forward," he said.

Reuters could not independently verify battlefield reports.

Ukrainian officials have imposed an information blackout to help operational security, but say that Russia has suffered much greater losses than Ukraine has during its new assault.

A regional official said Ukrainian forces had destroyed a Russian ammunition dump in occupied Kherson region, part of a weeks-long effort by Kyiv to disrupt Russian supply lines.

British defence intelligence said fighting had focused on Zaporizhzhia, western Donetsk and near Bakhmut, captured last month by Russian mercenaries after the war's longest battle.

"In all these areas, Ukraine continues to pursue offensive operations and has made small advances," it said on Twitter.

Russia's defence, it said, was "relatively effective in the south", with both sides suffering heavy casualties.