MOSCOW - Two powerful allies of Russian President Vladimir Putin said on Tuesday that they believed Ukraine was involved in the attack on a concert hall just outside Moscow that killed at least 139 people and wounded 180 others.

Ukraine has repeatedly denied any involvement and Islamic State, the militant group that once sought control over swathes of Iraq and Syria, claimed responsibility for the attack.

News outlet SHOT published a video of an exchange in which a reporter asked Nikolai Patrushev, the secretary of Russia's Security Council, whether it was "ISIS (Islamic State) or Ukraine?"

"Of course Ukraine," Patrushev replied.

Asked about the remark later, he said there were "many" indications of Ukraine's involvement.

Alexander Bortnikov, the director of the Federal Security Service (FSB), said that the gunmen had wanted to reach Ukraine where some people had been ready to spirit the attackers across the border.

"In general, we believe they are involved in this," Bortnikov told reporters about possible Ukrainian involvement, Russian news agencies reported. The FSB had information indicating the involvement of Ukraine in the attack, he said.

He offered no evidence for his assertions, but cited the alleged attempted escape of the gunmen towards Ukraine.

But Bortnikov said the FSB had yet to identify who specifically ordered the attack.

The remarks by Patrushev and Bortnikov offer an insight into hawkish thinking at the top of the Kremlin elite.

Putin said on Saturday in an address to the nation that all those responsible for the concert attack would be punished.

On Monday, he said that radical Islamists had carried out the attack, but said the attackers were trying to flee to Ukraine and questioned why Islamists would want to attack Russia at this particular time without being nudged to by others.

"We know that the crime was carried out by the hand of radical Islamists with an ideology that the Muslim world has fought for centuries," Putin said. "We want to know who ordered it." REUTERS