Ukrainian authorities said their forces targeted a Russian ammunition depot in southern Ukraine overnight, resulting in a massive explosion that killed 52.

The Ukrainian military's southern command said a rocket strike targeted the depot in Russian-held Nova Kakhovka, about 55 km east of the Black Sea port city of Kherson, which is also occupied by Russian forces.

The precision of the strike suggested Ukrainian forces used US-supplied multiple-launch High Mobility Artillery Rocket Systems, or HIMARS, to hit the area.

Ukraine indicated in recent days that it might launch a counteroffensive to reclaim territory in the country's south as Russia devotes resources to capturing all of the eastern Donbas region.

Russia's Tass news agency offered a different account of the blast in Nova Kakhovka, saying a mineral fertiliser storage facility exploded, and that a market, hospital and houses were damaged in the strike. Some of the ingredients in fertiliser can be used for ammunition.

Loading

Ukraine now has eight of the HIMAR systems, a truck-mounted missile launcher with high accuracy, and Washington has promised to send another four.

Russian offensive continues in Ukraine's south-east

Elsewhere in Ukraine, Russian shelling over the past 24 hours killed at least 16 civilians and wounded 48 more, Ukraine's presidential office said in its Tuesday morning update.

Cities and towns in five south-east regions came under Russian fire, the office said.

Nine civilians were killed and two more wounded in Donetsk province, which makes up half of the Donbas.

Russian rocket attacks targeted the cities of Sloviansk and Toretsk, where a kindergarten was hit, the presidential office said.

The death toll from a Russian rocket attack that struck a Donetsk apartment building Saturday rose to 38, Ukrainian officials said Tuesday afternoon.

The head of the Donetsk regional military administration, Pavlo Kyrylenko, said on social media earlier in the day that nine wounded people were rescued from the building in Chasiv Yar.

In Kharkiv, Ukraine's second-largest city, and its surrounding region, Russian strikes hit residential buildings, killing four civilians and wounding nine, Ukrainian officials said. 

"The Russians continue their tactics of intimidating the peaceful population of the Kharkiv region," Kharkiv Govenor Oleh Syniehubov wrote on Tuesday on Telegram.

Ukrainian authorities also said that Russian fire struck the southern city of Mykolaiv on Tuesday morning, hitting residential buildings.

Twelve people were wounded as the result of the Russian shelling, with some of the rockets hitting two medical facilities, regional governor Vitaliy Kim said on Telegram.

Air raid sirens sounded on Tuesday in the western city of Lviv — the first daytime sirens there in over a week — and in other areas of Ukraine as Russian forces continued to make advances.

In eastern Luhansk, "fighting continues near the villages" on the administrative border with neighbouring Donetsk, Luhansk Governor Serhiy Haidai said.

"The Russian army burns down everything in its way. The artillery barrage doesn't stop and sometimes continues for four to six hours on end," Mr Haidai said.

The British Defense Ministry's intelligence briefing said Russia had seized the Ukrainian town of Hryhorivka and continued to push toward the Donetsk province cities of Kramatorsk and Sloviansk.

"Russian forces are likely maintaining military pressure on Ukrainian forces whilst regrouping and reconstituting for further offensives in the near future," the intelligence briefing said.

AP