KYIV--Russia has opened a criminal investigation after gunmen shot dead 11 people at a military training ground near the Ukrainian border, authorities said on Sunday, as fighting raged in eastern and southern Ukraine.

Russia’s RIA news agency, citing the defense ministry, said two gunmen opened fire with small arms during a firearms training exercise on Saturday, targeting personnel who had volunteered to fight in Ukraine. RIA said the gunmen, who it referred to as “terrorists,” were shot dead.

The incident in the southwestern Belgorod region was the latest blow to Russian President Vladimir Putin’s “special military operation” in Ukraine. It came a week after a blast damaged a bridge linking mainland Russia to Crimea, the peninsula it annexed from Ukraine in 2014.

Russia’s defense ministry said the attackers were from a former Soviet republic, without elaborating. A senior Ukrainian official, Oleksiy Arestovych, said the two men were from the mainly Muslim Central Asian republic of Tajikistan and had opened fire on the others after an argument over religion.

Reuters was not immediately able to confirm the comments by Arestovych, a prominent commentator on the war, or independently verify casualty numbers and other details.

“As a result of the incident at a shooting range in Belgorod region, 11 people died from gunshot wounds and another 15 were injured,” Russia’s Investigative Committee said, announcing the criminal investigation. It gave no other details.

Some Russian independent media outlets reported that the number of casualties was higher than the official figures.

The governor of Belgorod region, Vyacheslav Gladkov, said no local residents were among those killed or wounded.

Two witnesses later told Reuters they had seen Russian air defense systems repelling air strikes in Belgorod.

Putin said on Friday Russia should be finished calling up reservists in two weeks, promising an end to a divisive mobilization in which hundreds of thousands of men have been summoned to fight in Ukraine and many have fled the country.

Belarusian President Alexander Lukashenko, a strong Putin ally, said last week that his troops would deploy with Russian forces near the Ukrainian border, citing what he said were threats from Ukraine and the West.

The Belarusian defense ministry in Minsk on Sunday said just under 9,000 Russian troops would be stationed in Belarus as part of a “regional grouping” of forces to protect its borders.

RUSSIAN SHELLING

Russian forces shelled Ukrainian positions on several fronts on Sunday, the General Staff of Ukraine’s Armed Forces said, with the targets including towns in Kharkiv, Donetsk and Kherson regions. Russian forces were trying to advance on Bakhmut in Donetsk region and in and around Avdiivka.

Intense fighting is taking place around Bakhmut as well as the town of Soledar, Ukrainian President Volodymyr Zelenskiy said on Sunday in his nightly video address.

“The key hot spots in Donbas are Soledar and Bakhmut,” Zelenskiy said. “Very heavy fighting is going on there.”

Bakhmut has been the next target of Russia’s armed forces in their slow move through the Donetsk region since taking the key industrial towns of Lysychansk and Sievierodonetsk in June and July. Soledar is located just north of Bakhmut.

Fighting has been particularly intense this weekend in the Donetsk and Luhansk regions, and the strategically important Kherson province in the south, three of the four provinces Putin proclaimed as part of Russia last month.

Shelling by Ukrainian forces damaged the administration building in the city Donetsk, capital of the Donetsk region, the head of its Russian-backed administration said on Sunday.

“It was a direct hit, the building is seriously damaged. It is a miracle nobody was killed,” said Alexei Kulemzin, surveying the wreckage, adding that all city services were still working.

There was no immediate reaction from Ukraine to the attack on Donetsk city, which was annexed by Russian-backed separatists in 2014 along with swathes of the eastern Donbas region.

Russia’s defence ministry said on Sunday its forces had repelled efforts by Ukrainian troops to advance in the Donetsk, Kherson and Mykolaiv regions, inflicting what it described as significant losses.

Russia also said it was continuing air strikes on military and energy targets in Ukraine, using long-range precision-guided weapons.

Reuters was unable to independently verify the battlefield reports.

In the city of Mykolaiv, residents queued on Sunday - as they do every day - to fill water bottles at a distribution point after supplies were severed by fighting early in the war.

“This is not war, this is a war crime. War is when soldiers fight with each other, but when civilians are being fought, it’s a war crime,” said Vadym Antonyuk, a 51-year-old sales manager, as he stood in line.

A spokeswoman for Ukraine’s Southern Military Command said Russian forces were suffering severe shortages of equipment including ammunition as a result of the damage inflicted last weekend on the Crimea Bridge.

“Almost 75 percent (of Russian military supplies in southern Ukraine) came across that bridge,” Natalia Humeniuk told Ukrainian television, adding that strong winds had also now stopped ferries in the area.

“Now even the sea is on our side,” Humeniuk said.

Putin blamed Ukrainian security services for the bridge blast and last Monday, in retaliation, ordered the biggest aerial offensive against Ukrainian cities, including the capital Kyiv, since the start of Russia’s invasion on Feb. 24.