The fallout from the attack on a prison in Olenivka where at least 53 Ukrainian prisoners of war were killed on Friday continues.

Mykhailo Podolyak, an adviser to President Volodymyr Zelenskyy, alleged on Sunday that images of the prison indicated that the blast came from within the building, which is under Russian control, according to an AP report.

Russian officials have claimed the building was attacked by Ukraine with the aim of silencing POWs who might be giving information about Ukrainian military operations.

Satellite photos taken before and after the attack show that a small, squarish building in the middle of the Olenivka prison complex was demolished, its roof in splinters.

Podolyak said on Twitter those images and the lack of damage to adjacent structures showed that the building was not attacked from the air or by artillery and contended the evidence was consistent with a hyperbaric bomb set off inside.

Here is a photo taken after the attack which is on the newswires

Isobel Koshiw

Isobel Koshiw reports for us from Kyiv:

Russia is moving large numbers of troops to Ukraine’s south for battles against the country’s forces through the newly occupied territories and Crimea, according to Ukraine’s deputy head of military intelligence.

If Russia won, it would try to capture more territory, said Vadym Skibitsky. “They are increasing their troop numbers, preparing for our counteroffensive [in Ukraine’s south] and perhaps preparing to launch an offensive of their own. The south is key for them, above all because of Crimea,” he said.

Russian troop movements come in response to Ukraine’s declared counteroffensive to liberate the southern occupied regions of Kherson and Zaporizhzhia.

Ukrainian forces have retaken dozens of villages and towns along the border, according to the region’s military governor, Dmytro Butrii, and are pushing towards Kherson’s regional capital.

Read more of Isobel Koshiw’s report from Kyiv: Ukrainian offensive forces Russia to bolster troops in occupied south 

The Ukrainian president, Volodymyr Zelenskiy, has paid tribute to Oleksiy Vadatursky, the owner of one of the country’s largest grain producing and exporting companies, after he was killed in shelling in Mykolaiv.

Vadatursky, the founder and owner of the agriculture company Nibulon, and his wife, were killed in their home, the local governor, Vitaliy Kim, said on Sunday.

Zelenskiy described Vadatursky’s death as “a great loss for all of Ukraine”, saying in a statement that the businessman had been in the process of building a modern grain market involving a network of transhipment terminals and elevators.

Three people were also wounded in the attacks on Mikolaiv, the city’s mayor, Oleksandr Senkevych, told Ukrainian television, adding that 12 missiles had hit homes and educational facilities.