Fighting raged Friday in southern Ukraine, but Russian leader Vladimir Putin claimed Kyiv's long-expected offensive was already failing.
Ukrainian President Volodymyr Zelensky, while praising the heroism of his country's soldiers, made no direct reference to what some observers believe is the much-awaited counter-offensive.
"For our soldiers, for all those who are in particularly tough battles these days, we see your heroism, and we are grateful to you for every minute of your life," Zelensky said in his daily address.
Ukrainian officials have said their forces are ready for a counter-offensive to claw back territory from Russia in the east and south but there would be no formal announcement when it began.
Earlier, Russian President Vladimir Putin said the counter-offensive had started but that efforts "so far have failed", after Moscow said it repelled several Ukrainian assaults.
Ukraine has said little about the clashes, but Moscow reported repelling attacks in the Zaporizhzhia and eastern Donetsk areas with ground and air forces.
"All counter-offensive efforts so far have failed but the offensive potential of the Kyiv regime still remains," Putin said in a video, as Washington announced a new $2.1-billion package of military aid for Ukraine.
Meanwhile the human cost climbed after the destruction of the Kakhovka dam unleashed flooding along the Dnipro River in a different part of southern Ukraine, where a massive explosion was detected as the dam collapsed.
Moscow says clashes have intensified since Thursday in the Zaporizhzhia region, particularly around the small town of Orikhiv and towards the larger city of Tokmak, around 40 kilometres (25 miles) to the south in Russian-occupied territory.
Zaporizhzhia is home to Europe's largest nuclear power plant, which relies on the waters of the Dnipro for its cooling ponds.
- New US aid -
A Ukrainian military success in the Zaporizhzhia region would enable its forces to break through the land bridge that connects Russia with the Crimean peninsula it annexed from Ukraine.
That would be a major reversal for Moscow.
The Russian army has in recent months strengthened its front lines in the region, digging kilometres of trenches and fortifying defences.
The Russian army said it had repelled four attacks -- "carried out by forces of up to two battalion tactical groups, reinforced with tanks" -- near the villages of Levadnoye in the Zaporizhzhia region and in the village of Novosleka in the eastern region of Donetsk.
It said it had used troops and air force to repel two attacks near Novodanilovka and Malaya Tokmachka in the Zaporizhzhia region.
The increase of fighting in the south has been seen by many observers as a sign that the counter-offensive is already happening, or is about to start.
Kyiv, however, said the main centre of combat was still in eastern Ukraine, while providing few details on the situation in the south.
Ukrainian officials have said their forces are ready for the long-expected counter-offensive but there would be no formal announcement when it begins.
Kyiv's forces were bolstered with news of the new United States package, which will include missiles for Patriot air defence systems, artillery rounds, drones and laser-guided rocket system munitions.
It took to $40.4 billion the value of military supplies the United States has provided Ukraine since early 2021, most of it since Russia invaded the country on February 24, 2022.
- Dam breach casualties -
The White House said on Friday Russia was receiving materials from Iran to build a drone factory on its territory that "could be fully operational early next year".
Washington estimates that Russia has received hundreds of attack drones as well as related equipment from Iran to aid Moscow's war on Ukraine.
Parallel to the fresh fighting, the destruction of the major Russian-held dam on the Dnipro river on Tuesday left 600 square kilometres of the region under water.
Emergency services were racing to rescue people stranded by the flood-swollen waters of the Dnipro, which have forced thousands to flee.
Russian-installed authorities in southern Ukraine on Friday reported more casualties from the flood triggered by the dam's destruction, and said the water could keep rising for more than a week.
"Unfortunately, there are casualties... Their number has grown to eight people," the Moscow-installed head of the Kherson region, Vladimir Saldo, said on Telegram.
The water, which flooded 22,273 homes in 17 settlements, could "keep rising for up to 10 days".
More than 5,800 people were evacuated since the flood was unleashed on Tuesday, Saldo said, including 243 children.
At least five people died and 13 are missing in flooding, Ukrainian Interior Minister Igor Klymenko said on Friday.
- Explosives breached dam -
Ukraine and Russia have traded blame for the destruction of the Kakhovka dam but European Union foreign policy chief Josep Borrell said "everything indicates" Moscow was behind the breach.
"The dam was not bombed. It was destroyed by explosives installed in the areas where the turbines are located. This area is under Russian control," Borrell told Spanish public television.
Norway's seismological institute said it had detected "an explosion" at the site and time the dam was destroyed, supporting suggestions the breach did not occur as a result of damage incurred during months of heavy bombing.
Ukrhydroenergo, the dam's operator, said it was most likely mined from the inside.
Ukrainian authorities said water levels in a reservoir which had been created by the Kakhovka dam had fallen "below the critical point of 12.7 metres (42 feet)".
They said the reservoir was no longer able to supply households and the cooling ponds at the huge Zaporizhzhia nuclear power plant.
However late on Thursday the International Atomic Energy Agency (IAEA) said the nuclear plant was continuing to receive water from the reservoir after the dam was damaged.
The plant's six reactors have been shut down but they still need cooling water to ensure there is no nuclear disaster.
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