President Vladimir Putin of Russia says Ukraine had a hand in the terrorist attack at Crocus City Hall in Moscow, the country’s capital.
As many as 133 people have now been confirmed dead from the shooting incident. The death toll was earlier put at 113.
The Islamic State (ISIS) claimed responsibility for the attack which is Russia’s deadliest in decades but did not provide evidence.
But Putin, in a speech on Russian television on Saturday, said the gunmen were helped by someone in Ukraine.
“They tried to hide and moved toward Ukraine, where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the border,” Putin said.
“Our military services, our emergency services … our investigators are working on finding out … who gave them transportation, … who gave them weapons.
“We will stand united against this common enemy, international terrorism, no matter where it shows its ugly head.”
The Russian leader did not provide evidence for his reference to Ukraine but vowed that “all the perpetrators, organisers and those who ordered this crime will be justly and inevitably punished — whoever they are, whoever is guiding them”.
PUTIN SAYS ALL FOUR GUNMEN ARRESTED
In his address, Putin said 11 people had been detained, including the four gunmen.
Russia’s Federal Security Service said the gunmen had contacts in Ukraine and were captured near the border.
The agency did not provide proof of this. It said the suspects were being transferred to Moscow.
Andrei Kartapolov, a Russian lawmaker, said the country must deliver a “worthy, clear and concrete” reply on the battlefield if Ukraine is involved.