TALLINN, Estonia (AP) — The head of Russia’s national security council on Wednesday contended that the United States shares blame for the attack by gunmen on a Moscow concert hall that killed 145 people, even though a branch of the Islamic State group has claimed responsibility.

Since the March 22 attack at the Crocus City Hall, the deadliest on Russian soil in two decades, Russian officials including President Vladimir Putin have repeatedly claimed, without presenting evidence, that it was organized by Ukraine, which has been fighting a Russian invasion for more than two years.

An affiliate of the Islamic State claimed responsibility for the attack and Kyiv has consistently denied involvement.

“They are trying to impose on us that the terrorist act was committed not by the Kyiv regime, but by supporters of radical Islamic ideology, perhaps members of the Afghan branch of IS,” security council head Nikolai Patrushev said at a meeting in the Kazakhstan capital Astana of security councils of the Shanghai Cooperation Organization. The SCO is a nine-country regional security and economic bloc that includes China, India and Iran.

“However, it is much more important to quickly establish who is the customer and sponsor of this monstrous crime. Its traces lead to the Ukrainian special services. But everyone knows that the Kyiv regime is not independent and is completely controlled by the United States,” Patrushev said.

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Four suspected gunmen were captured the day after the attack in the Bryansk region, which borders Ukraine. Putin and other officials claim that the gunmen had arranged for passage into Ukraine. Six other suspected accomplices have also been arrested.

Russia’s emergencies ministry gave the death toll in the attack as 144, but children’s rights ombudsman Maria Lvova-Belova said Wednesday that a sixth child injured in the attack had died.

The attack came two weeks after the United States Embassy in Russia issued a warning that it was monitoring reports of planned terrorist attacks on public targets. The U.S. State Department said information about the planned attacks was passed on to Russian officials.

Putin spokesman Dmitry Peskov on Wednesday declined comment in a conference call on a report in the Washington Post that U.S. officials had specifically identified Crocus City Hall as a potential target, saying that was a matter for security services.

Foreign Ministry spokeswoman Maria Zakharova disdained the report, telling journalists at a briefing that “I would really like to ask you to receive factual material on this topic from the American side. That is, when and to whom did they transmit this information.”

Also Wednesday, the Russian prosecutor-general’s office sent information requests to the U.S., Germany, France and Cyprus over Western countries’ potential involvement in terrorist attacks on Russia, state news agency Tass reported.