Russian President Vladimir Putin says a Ukrainian sabotage group entered a Russian border region on Thursday and opened fire on civilians in a "terrorist act".

The governor of Bryansk region said "saboteurs from Ukraine" had fired at a civilian car in Lyubechane, a border village, killing two men and wounding a 10-year-old boy.

Kyiv strongly denied the Russian claim.

The alleged incident has not been independently verified.

Mykhaylo Podolyak, an adviser to Ukraine's President Volodymyr Zelensky, tweeted that it was "a classic deliberate provocation". "RF [Russia] wants to scare its people to justify the attack on another country," he said.

Russia has previously reported some Ukrainian missile and drone strikes on Russian border areas, including Bryansk region. But there have been no confirmed reports of Ukrainian ground forces infiltrating Russia.

Russia's Federal Security Service (FSB) said FSB forces and regular troops on Thursday clashed with "Ukrainian nationalists" who had crossed into Russia and taken hostages.

The FSB said the "nationalists" were then hit with a massive Russian artillery strike and pushed back into Ukraine. They left a large cache of explosives in the village, the FSB alleged.

When Russia launched its large-scale invasion of Ukraine in February 2022 President Putin branded the Kyiv government "nationalists" and "neo-Nazis", arguing that Russia had to act against them.

President Zelensky was democratically elected, has Jewish origins and has no far-right politicians in his government.

Speaking on Russian state TV on Thursday President Putin said "today they committed another terrorist act, another crime, penetrated the border area and opened fire on civilians".

"They saw that it was a civilian car, that civilians and children were sitting there, and opened fire. It is exactly such people who set themselves the task of depriving us of historical memory. They will achieve nothing, we will put the squeeze on them," he said.

A video has appeared online claiming to show members of the Ukraine-based Russian Volunteer Corps (RVC) outside a local clinic. One armed man in the video, posted on Telegram, says they crossed into Russia.

The investigative journalism group Bellingcat Monitoring describes the RVC as "a unit officially formed last year made up primarily of anti-Putin, anti-Kremlin Russian far-right figures active in Ukraine".

A Bellingcat expert, Michael Colborne, has identified one of the men in the video as RVC leader Denis Kapustin, who also uses the surname Nikitin.

"This RVC seems to do very little actual fighting, or at least serious fighting, and Kapustin may have physical combat sports training but he is not from any sort of military background," Mr Colborne told the BBC.

In a text post with the video the RVC said it "entered Bryansk region to show our compatriots that there is hope, that free Russians carrying arms can fight the regime".

Commenting on the RVC claim, a Ukrainian military intelligence official, Andriy Yusov, said "these are people who are fighting with arms against the Putin regime and those who support him... Perhaps Russians are beginning to wake up, realise something and take some concrete steps".

This week Mr Putin accused Ukraine and Western spies of intensifying operations inside Russia. Russian officials said a drone crashed in the Kolomna district just 100km (62 miles) from Moscow - though it was not confirmed to be Ukrainian - while two Ukrainian drones were allegedly shot down in southern Russia.

Previously Russia said drones had attacked an airbase in southern Russia used for launching bomber strikes on Ukraine. Kyiv has not claimed drone attacks inside Russia, accusing the Kremlin of propaganda.