At least 13 people were injured in the city of Kursk after debris from a destroyed Ukraine-launched missile fell onto a nine-storey residential building, officials of the Russian border Kursk region said on Sunday.

Moscow’s forces are in their sixth day of intense battles against Kyiv’s largest incursion into Russian territory since Russia launched a full-scale invasion on its smaller neighbour, with local authorities rushing to evacuate areas at risk.

Alexei Smirnov, Kursk’s acting governor, said in a post on the Telegram messaging app that two of the injured were in serious condition.

Residents of the building were to be evacuated to a temporary accommodations centres, Kursk Mayor Igor Kutsak said on Telegram. He added that the whole city was under air raid alerts.

Kutsak posted a photo of a residential building with blown out windows and damaged balconies and facade of a residential building at night.

Reuters could not independently verify the reports from Kursk. There was no immediate comment from Ukraine.

Both Kyiv and Moscow deny targeting civilians in their attacks in the war, which has killed thousands of people and misplaced millions of Ukrainians, and has no end in sight.

Ukrainian President Volodymyr Zelensky acknowledged on Saturday that Ukrainian forces were fighting in Kursk, saying the operation was part of Kyiv’s attempt to restore justice after Russia invaded the country in 2022.

In his nightly video address, Zelenskyy said he had discussed the operation with top Ukrainian commander Oleksandr Syrsky.

“Today, I received several reports from commander-in-chief Syrsky regarding the frontlines and our actions to push the war onto the aggressor’s territory,” he said.

“I am grateful to every unit of the defence forces for ensuring that. Ukraine is proving that it can indeed restore justice and ensure the necessary pressure on the aggressor.”

The Ukrainian president’s comments came hours after Russia said it had introduced “anti-terrorism measures” in Kursk and two other regions bordering Ukraine in response to the operation.

The measures by the National Anti-Terrorism Committee in Kursk, Belgorod and Bryansk included limits on transport in specific areas, tightened security around sensitive sites, and wiretaps of telephone and other communications, according to the RIA news agency.

The statement said the decision, taken by Alexander Bortnikov, the head of the Federal Security Service (FSB), was in response to Ukraine’s “unprecedented attempt to destablise the situation in a series of regions”.