President Vladimir Putin tried to link Ukraine to the "terrorist" massacre at a concert hall outside Moscow and said those behind the attack will be "justly and inevitably punished," as Russian officials raised the death toll to 133, reports said Saturday.

Ukraine has vehemently denied any involvement in the mass shooting.

Russia said it had detained 11 people, including the four suspected of carrying out the shooting at the Crocus City Hall on Friday, and claimed they were captured in western Russia while on their way to Ukraine.

Putin, in his first remarks Saturday about the rampage, said the four had hoped to cross the border.

"They tried to hide and moved towards Ukraine, where, according to preliminary data, a window was prepared for them from the Ukrainian side to cross the state border," Putin said in an address to the nation, Reuters reported.

The Russian leader said the culprits will be punished.

"All the perpetrators, organizers and those who ordered this crime will be justly and inevitably punished. Whoever they are, whoever is guiding them," Putin said. "We will identify and punish everyone who stands behind the terrorists, who prepared this atrocity, this strike against Russia, against our people."

Gunmen wearing camouflage and toting automatic weapons opened fire on people attending a concert by the Russian rock band Picnic, firing at concert-goers at random and tossing incendiary devices into the crowd that eventually engulfed the auditorium in flames. 

Russia's Investigative Committee said Saturday that at least 133 people had been killed in the attack and hundreds more wounded.

Ukraine, which has been battling Russian forces since Putin invaded the country in Feb. 2022, has continued to deny accusations they were involved in the attack. 

"Ukraine was of course not involved in this terror attack. Ukraine is defending its sovereignty from Russian invaders, liberating its own territory and is fighting with the occupiers' army and military targets, not civilians," Andriy Yusov, a spokesman for Ukraine's military intelligence, told Reuters.

Mykhailo Podolyak, an aide to Ukrainian President Volodymyr Zelensky, also shot down the claims.

"Ukraine has never resorted to the use of terrorist methods," he posted on social media, the AP reported. "Everything in this war will be decided only on the battlefield."

An affiliate of the Islamic State terror group in Afghanistan, ISIS-K, has claimed responsibility, claiming through its news agency that it was attacking "Christians" at the concert. 

A U.S. intelligence official told the Associated Press that U.S. intelligence agencies have also confirmed the attack was carried out by ISIS.

The official told the wire service that U.S. intelligence agencies had compiled information recently that the terror branch was plotting an attack in Moscow.

American officials shared their information with Russian officials earlier this month, but Putin dismissed the warning as "provocative statements" just days before the attack.

"I'll remind you of recent, let's say directly, provocative statements of certain official Western structures about potential terror attacks in Russia," Putin said.

"All of this looks like obvious blackmail and an attempt to intimidate, destabilize our country," he said.