At least 50 people were killed and more than 180 wounded on Tuesday when Russia struck a military institute in the central town of Poltava with two missiles, President Volodymyr Zelensky said, the war’s deadliest single attack so far this year.

Zelensky said in a video that Russian forces struck with two ballistic missiles, damaging a building of the Military Institute of Communications. He ordered a full and prompt investigation.

“The Russian scum will definitely be held accountable for this strike,” Zelensky said on the Telegram messaging app.

According to the foreign ministry, the type of weapons used left little time for people to find cover once the air alert had sounded.

Photographs posted on social media in Ukraine showed several bodies lying on the ground covered in dust and debris, with the badly damaged side of a large building behind them. Reuters could not immediately verify the images.

“One of the institute’s buildings was partially destroyed, and many people were trapped under the rubble,” the defence ministry said on Telegram.

“Thanks to the coordinated work of rescuers and medics, 25 people were rescued, 11 of whom were taken from the rubble. The rescuers are currently continuing their work.”

Moscow had yet to comment on the attack.

Russia has intensified its missile and drone attacks on Ukraine two-and-a-half years into the full-scale war.

Last week Ukraine was pummelled with the heaviest bombardment to date, and on Monday ballistic and cruise missiles targeted Kyiv causing loud explosions.

Ukraine also targeted Russia with more than 158 drones at the weekend, damaging an oil refinery near Moscow and a power station. Zelensky repeated his calls for more western air defences and urged allies to allow their long-range weapons to be used for strikes deeper into Russian territory in order to protect Ukraine.

“We keep telling everyone in the world who has the power to stop this terror: air defence systems and missiles are needed in Ukraine, not in a warehouse somewhere.

“Long-range strikes that can protect us from Russian terror are needed now, not some time later. Unfortunately, every day of delay means loss of life.”

In Poltava, some 300 km southeast of Kyiv and 120 km to the nearest Russian border, governor Filip Pronin said that many residents had donated blood for the injured. Local authorities announced three days of mourning.

The identities of the victims were not immediately disclosed.

Serhiy Beskrestnov, a prominent Ukrainian Telegram blogger followed by many radio, communications and Electronic Warfare specialists in Ukraine’s military, posted a tribute to “my signals operator comrades”.

Fighting has intensified over the past month, with Russian forces advancing in heavy battles in eastern Ukraine, while Kyiv’s troops have mounted their first large-scale cross-border assault into a Russian region, for which Moscow has vowed to retaliate.