Russia called for an urgent Security Council meeting after a group of armed men claimed to have staged the first cross-border attack by Ukrainian troops. 

The obscure group, Russian Volunteer Corps, claims to be fighting alongside the Ukrainian army against the Russian armed forces.

Last month, Ukraine warned of a false flag operation in the same area, saying that Moscow could use it as an excuse to further escalate the war.

Vladimir Putin at a televised meeting with teachers on Thursday afternoon called the incident on the border a terrorist attack.

"Yet another crime," he said.

"They infiltrated the border area and opened fire on civilians. They saw it was a civilian car, that there were children. They still fired on it."

His spokesman earlier said the president would hold an urgent meeting of the Security Council to discuss the incident.

Russia’s intelligence agency claimed a group of Ukrainian saboteurs attacked two border villages while Kremlin-linked outlets reported that hostages have been taken.In a statement, the FSB said a border area in the Bryansk region was attacked by “armed Ukrainian nationalists” and Russian troops were clashing with them.Later on Thursday, the FSB said the area was under its control and that law enforcement officers were working to de-fuse a number of explosive devices left there.