Russian forces have stepped up their battle to seize one of the dwindling number of cities in embattled eastern Ukraine not already under their control, while continuing to fire on towns and villages in the country’s north and south.

Ukrainian officials said on Saturday that Russian shelling had collapsed balconies and blown out windows in the southern region of Mykolayiv, injuring at least nine civilians.

A five-storey apartment building and private homes in the town of Voznesensk were badly damaged, the Black Sea region’s governor said.

Vitaliy Kim wrote in a Telegram post: “As of 1.30pm (local time) – nine wounded, including four children. All children in a serious condition. Ages range from three to 17.”

He added that a young girl lost an eye as a result of Saturday’s attack.

Reflecting the broadening frontlines of the nearly six-month war, a Ukrainian air strike hit targets in the largest Russian-occupied city in the southern Zaporizhzhia region, according to Ukrainian and Kremlin-backed local officials.

The Ukrainian mayor of Melitopol said preliminary reports pointed to “a precise hit” on a Russian military base. The head of the Kremlin-backed administration said the attack damaged residential areas and slightly injured one civilian.

In its daily update, the General Staff of the Armed Forces of Ukraine said intensified combat took place around Bakhmut, a small city whose capture would enable Russia to threaten the two largest remaining Ukrainian-held urban centres in the eastern Donbas region.

Bakhmut has for weeks been a key target of Moscow’s eastern offensive as the Russian military tries to complete a months-long campaign to conquer all of the Donbas, an industrial region that borders Russia where pro-Moscow separatists have self-proclaimed a pair of independent republics.

A local Ukrainian official reported sustained fighting on Saturday morning near four settlements on the border between Luhansk and Donetsk provinces, which together make up the contested region.

Russian forces overran nearly all of Luhansk last month and since then have focused on capturing Ukrainian-held areas of Donetsk.

Russian shelling killed seven civilians on Friday in Donetsk province, including four in Bakhmut, governor Pavlo Kyrylenko wrote on Saturday on Telegram.

Taking Bakhmut would give the Russians room to advance on the province’s main Ukrainian-held cities, Kramatorsk and Sloviansk.

The General Staff update said Sloviansk and Kramatorsk were also targeted on Friday along with the Kharkiv region to the north, home to Ukraine’s second-largest city.

Neither Moscow nor Kyiv commented on the air strike aimed at Russian-occupied Melitopol in southern Ukraine.

Earlier on Saturday morning, The Russian Defence Ministry’s spokesman, Igor Konashenkov, claimed pro-Russia forces had shot down Ukrainian shells near the city, as well as near a key power station in the Kherson region, which the Russians seized early in the war.

The head of the Kremlin-installed administration in Melitopol confirmed the city had come under Ukrainian fire.

Galina Danilchenko said on Telegram: “During the night, the Kyiv regime launched two attacks on our beautiful Melitopol, on residential areas of the city. Russian air defence systems shot down missiles, but as a result of the shelling, the houses of residents on (two) streets were partially destroyed and damaged.”