Russia expects Washington and its allies to cooperate with its investigation aimed at identifying the masterminds behind the deadly Moscow terror attack that took place in March, the nation’s ambassador to the UN, Vassily Nebenzia, said on Friday.

The attack on the Crocus City Hall concert venue, which is located just outside Moscow, claimed more than 140 lives. Four gunmen stormed the place, shooting everyone in sight before setting it on fire. A total of 11 suspects were arrested in the wake of the rampage, including the four alleged assailants.

Russian officials described the perpetrators as radical Islamists but stated that the crime may have been organized by Ukrainian security services, who used them as proxies. On Friday, Nebenzia said that the extensive effort made by the US and its allies to draw attention away from Ukraine only reinforces suspicions about Western involvement.

“Amid such relentless attempts to pin the blame on ISIS and shield Kiev at any cost… a question about Western security services’ involvement in orchestrating this terrorist attack remains open,” the diplomat said, referring to Islamic State (IS, formerly ISIS), an international terrorist group that claimed responsibility for the massacre. The Western media repeatedly pointed to those claims while reporting about the incident.

Moscow has “no doubts” that Ukraine was “directly involved in this despicable and egregious crime,” Russia’s UN envoy said, adding that investigators already have enough evidence for such a conclusion.

Earlier in April, Russia’s Investigative Committee said that a potential link between Ukrainian security services and the March attack had been uncovered. The statement cited “significant evidence” of Kiev’s involvement but did not provide any specific details.

Investigators recently claimed to have found a money trail linking the alleged terrorists to Ukrainian nationalists. Russia’s FSB security agency also released records of interrogations of the suspected gunmen, who claimed that they had been given instructions to flee towards the Ukrainian border after the strike.

“We expect our Western colleagues to cooperate on detaining the masterminds behind the Crocus City Hall terrorist attacks and bringing them to justice,” Nebenzia said on Friday, adding that Moscow also would like to see the West aid its investigation of the Nord Stream pipelines explosions that took place in autumn 2022. After all, Western nations “unequivocally condemned” both attacks, the diplomat added.