Updated with Defense Ministry spokesperson comments and new death toll.Russia said four people were killed and several injured in a Sunday strike on a city near the border with Ukraine, the most deadly attack inside Russia since the start of the invasion of its western neighbor.The explosions, which occurred in the early hours of Sunday morning, damaged 11 apartment blocks and 39 houses in Belgorod, regional governor Vyacheslav Gladkov said on Telegram.“A series of loud explosions were heard in Belgorod.

A private house is on fire on 23 Mayakovskaya Street.

All emergency services are working at the scene,” Gladkov posted shortly after 4 a.m on Telegram.A video of one explosion in Belgorod showed a huge fireball rising into the night sky behind what appeared to be apartment blocks.Russian towns and cities next to the Ukrainian border have experienced a string of such incidents since the beginning of the invasion in February, but the casualty count Sunday was the highest yet recorded."Russian ant-aircraft defences shot down three Tochka-U cluster missiles launched by Ukrainian nationalists against Belgorod," Russia's defense ministry spokesman, Igor Konashenkov, said Sunday.

"After the destruction of the Ukrainian missiles, the debris of one of them fell on a house".Another two bodies were pulled from the rubble Sunday morning, news outlet Baza reported.

 Dozens of Ukrainian civilians were killed in Russian attacks on Ukrainian cities last week, including a rocket attack on a shopping mall in Kremenchuk and a strike on apartment blocks in Odesa Region.

Reports of explosions on Russian territory have become more common since Moscow’s forces withdrew from Kyiv in late March and the Ukrainian army launched a counteroffensive near the city of Kharkiv.Kyiv has not claimed responsibility for any attacks on Russian territory, but has also not formally denied being behind them.

Two Ukrainian drones were shot down by air defense systems over Russia’s Kursk region Sunday morning, Kursk region governor Roman Staravoit said on Telegram.AFP contributed reporting.