Ukraine says Russian strike on training camp killed 3 soldiers

 Destroyed building of the Bilenkivska correctional colony following an air attack in Bilenke, Zaporizhzhia region, amid the Russian invasion of Ukraine.[AFP]

A Russian strike on a military training camp killed at least three Ukrainian soldiers on Tuesday, following an overnight offensive in the south that killed a pregnant woman and a dozen prisoners.

The Kremlin has come under intense pressure to end its war on Ukraine, now in its fourth year, with US President Donald Trump issuing a 10-day ultimatum to act or face sanctions.

On social media, the Ukrainian army said a Russian missile hit one of the ground force's training units, without specifying the location.

At least "three servicemen are dead and 18 wounded," it said Tuesday.

Over the previous night, a series of Russian attacks killed at least 25 civilians, including a 23-year-old pregnant woman and more than a dozen inmates at the Bilenkiska penal colony in southern Zaporizhzhia region.

Ukrainian President Volodymyr Zelensky accused Russia of deliberately targeting the prison, which the justice ministry said killed 17 people and wounded another 42.

The Kremlin denied the claim, with spokesman Dmitry Peskov telling reporters, "the Russian army does not strike civilian targets".

The attacks came hours after Trump said he was shortening the deadline for Russian President Vladimir Putin to halt the war from 50 days to 10-12 days.

Hours later, Trump solidified the 10-day timeline, threatening "tariffs and stuff", while also conceding to not knowing if the measures would work.

Peskov said Moscow had "taken note", and that it remained "committed to the peace process to resolve the conflict around Ukraine and secure our interests".

'Prolonging the war'

The Ukrainian air force said Russia launched 37 drones and two missiles overnight into Tuesday, with 32 of the drones successfully downed.

Zelensky also accused Russia of targeting a hospital in the town of Kamyanske in Dnipropetrovsk region, killing three people and wounding 22.

Other Russian attacks killed six in the Kharkiv region, where the city of Kharkiv faced another attack at dawn on Wednesday.

"Putin is rejecting a ceasefire, avoiding a leaders' meeting and prolonging the war," Ukrainian Foreign Minister Andriy Sybiga wrote on social media.

"He will only end his terror if we break the spine of his economy," he added, calling on Western allies to impose sanctions.

Kyiv has been trying to repel Russia's summer offensive, which has made fresh advances into areas largely spared since the start of the invasion in February 2022.

The Russian defence ministry claimed advances across the front line on Tuesday, saying its forces had taken two more villages one in the Donetsk region, and another in Zaporizhzhia.

Tuesday's prison strike fell on the third anniversary of an attack on the Olenivka detention centre in Russian-occupied Donetsk.

Ukraine and Russia traded blame for that night time strike, which Kyiv said killed dozens of soldiers who had laid down arms after a long Russian siege of the port city of Mariupol.