Russian intelligence agency Federal Security Service (FSB) on Saturday said the Moscow attackers were heading to Russia's Ukrainian border and they had contacts on the Ukrainian side, reported Interfax.
The agency said the attack was carefully planned before being executed. However, Russia is yet to make public any evidence of a Ukrainian connection in the attack.
Ukraine presidential adviser Mykhailo Podolyak said Kyiv had "nothing to do" with the attack. "Let's be straight about this: Ukraine had absolutely nothing to do with these events," Podolyak said.
However, Russia has accused the US of withholding information about the involvement of Ukrainians in the attack.
Responding to a question on Ukrainians' involvement in the terror attack, US National Security Council spokesperson John Kirby said, "There is no indication at this time that Ukraine, or Ukrainians, were involved in the shooting. I would disabuse you at this early hour of any connection to Ukraine."
Alexander Bortnikov, the head of FSB, revealed that four terrorists directly involved in the attack were among the 11 people detained by the agency, reported Tass, Russia's state news agency.
The revelation comes as the death toll in the Moscow attack on Friday rose to 115. Reports said that 143 others were also injured in the attack. The attack in western Moscow occurred after assailants stormed into a concert hall and opened fire on the crowd. The hall was up in flames and the roof collapsed, raising the casualty.
ISIS-K has claimed responsibility for the attack, which is the deadliest in Russua in years. This is not the first attack by the Islamic State on Russia. In 2015, a bomb planted by the terror group downed a Russian passenger plane over Egypt's Sinai, killing all 224 aboard.
