Kyiv said on Tuesday it had launched artillery barrages that destroyed a Russian arms depot and carried out a "special operation" to free military captives in the Moscow-controlled Kherson region.

The bombardments in the south came as Washington and the EU announced nearly $3 billion in combined aid for Ukraine.

Ukrainian military officials said the strikes had destroyed artillery, armoured vehicles "and a warehouse with ammunition" in the town of Nova Kakhovka.

Russian-backed authorities accused Ukraine, however, of damaging civilian infrastructure and killing at least seven people, a toll that could not be independently verified.

"Warehouses were hit, as were shops, a pharmacy, petrol stations and even a church," the head of the city's Moscow-backed administration, Vladimir Leontiev, said on social media.

Ukrainian military intelligence said separately its forces had freed five captives in a "special operation" in Kherson, including a military serviceman and former police officer, without specifying when.

The Ukrainian army has for several weeks been waging a counter-offensive to recapture Kherson, which was taken by Russian troops early in the invasion of Ukraine.

Military analysts are crediting newly arrived weapons systems from the West for attacks deeper into Russian-controlled territory across the front line.

EU member states, which have been supplying Ukraine with military support, on Tuesday approved one billion euros in financial help for Kyiv, billing it as the first instalment of a promised nine-billion-euro rescue package agreed in May.

The United States separately announced $1.7 billion for Ukraine to help fund recovery.

"This aid will help Ukraine's democratic government provide essential services for the people of Ukraine," Treasury Secretary Janet Yellen said of the funds, which are part of a $7.5 billion aid package signed by President Joe Biden in May.

Moscow struck back across Ukraine, with officials in the southern city of Mykolaiv saying Russian forces had bombed two medical facilities and homes, injuring 12 people. (AFP)