Russia’s FSB security service said Thursday it had arrested three more people suspected of helping plot last month’s deadly terror attack on a Moscow concert hall, state media reported.

The Islamic State (IS) group has claimed responsibility for the massacre, in which more than 140 were killed when gunmen stormed the Crocus City Hall venue on the outskirts of Moscow before setting the building on fire.

The FSB said Thursday it had arrested three in Moscow, the Urals city of Yekaterinburg and Omsk in Siberia for financing and recruiting for the attack.

“Two of those detained transferred money for the purchase of firearms and vehicles used in the terror attack, and a third was directly involved in recruiting accomplices of the terror attack and financing its perpetrators,” the Interfax news agency quoted the FSB as saying in a statement.

State media published footage showing FSB agents making the arrests.

Two were foreign citizens and one was Russian, the FSB said.

Russia has arrested more than a dozen people it said were involved in the attack, including the four gunmen, all citizens of Tajikistan.

The IS group has claimed responsibility for the attack on multiple occasions, but Moscow has repeatedly tried to say it was “ordered” by Kyiv or the West.

“We have every reason to believe that the main goal of those who ordered the bloody, horrific terror attack in Moscow was to inflict damage on our unity,” Russian President Vladimir Putin said Thursday.

He said “Islamic fundamentalists” had no reason to target Russia.

Ukraine and Western leaders have repeatedly denied any connection to the attack and said Moscow is trying to exploit the tragedy.