The president Vladimir Putin claimed today Thursday that Russia was hit by “terrorist attack” in the southern Bryansk region bordering Ukraine and vowed to crush what he called a Ukrainian saboteur group that opened fire on civilians.

Ukraine accused Russia of staging a fake “provocation” but also appeared to hint that some form of operation was indeed being carried out by Russian rebels.

Amid reports of bombings and sporadic sabotage, Russia’s border regions have become increasingly volatile since Moscow invaded Ukraine a year ago in what it called a “special military operation.”

In a televised address, Putin accused the group of opening fire on civilians in a car, including children. The governor of Bryansk, Alexander Bogomaz, said that the attack killed two people and injured an eleven-year-old child.

“They won’t accomplish anything. We’re going to crush them,” Putin threatened, claiming the group was made up of the kind of people who want to steal Russia’s history and language.

The FSB Federal Security Service initially said the army and FSB were trying to neutralize “an armed group of Ukrainian nationalists” who had crossed the border.

The FSB later reported that the situation is under the control of law enforcement agencies. He said that a large number of explosive devices had been found, and that their clearance was in progress. He made no reference to reports by state news agencies that hostages had been taken.

In two videos circulating online, armed men who call themselves “Russian Volunteer Corps” they said they crossed the border to fight the “damned regime of Putin and the Kremlin” as they called it.

Calling themselves Russian “liberators”, the gunmen called on Russians to take up arms and rise up against the authorities. They said they did not open fire on civilians.

Reuters is currently unable to confirm the authenticity of the video.

Kremlin spokesman Dmitry Peskov told reporters that law enforcement agencies would determine who was responsible and that Putin was being briefed by security chiefs about the situation.

Kiev accuses Moscow of “provocations”

The adviser to the Ukrainian president Mihailo Podoliak tweeted: “Story about Ukrainian sabotage group in RO (Russian Federation) is classic deliberate provocation.”

Podoliak said Russia “wants to scare its own people in order to justify attacking another country and increasing poverty after a year of war.”

A spokesman for the Ukrainian military intelligence service hinted that the invention of the saboteur group is an indication of internal strife within Russia.

“These are people who are fighting Putin’s regime and those who support it with weapons in their hands… Maybe the Russians will start to wake up, realize something and take some concrete steps,” Andriy Yusov told Ukrainian media outlet Hromadske.

British military intelligence said on Wednesday that Russia was launching drone attacks in Ukraine from the Bryansk region, which is located in northern Ukraine and is closer to the capital Kiev than other launch sites.

Russia has accused Ukrainian saboteurs of breaking into Bryansk before. In December, the FSB reported that a four-member Ukrainian “saboteur team” was “neutralized” while attempting to enter the area.

Putin urged the FSB this week to step up measures against espionage and what he called terrorist threats from Ukraine and the West.

“Your mission is to raise obstacles in the way of saboteur groups, to stop attempts to illegally transfer weapons and ammunition to Russia,” he said in a speech yesterday Tuesday.