A group of Russian militants involved in bombings in Europe is a white supremacist terrorist group, the State Department’s top counterterrorism official announced Monday.

“This is the first time the United States has ever designated white supremacist terrorists, illustrating how seriously this administration takes the threat,” Counterterrorism Coordinator and Ambassador Nathan Sales told reporters. “We are taking actions no previous administration has taken to counter this threat.”

The designations target the Russian Imperial Movement, which reportedly fought alongside unmarked Russian forces when Russian President Vladimir Putin ordered the 2014 invasion of Ukraine. Sales, who explained that the group “provides paramilitary-style training to neo-Nazis and white supremacists,” blamed that movement for a series of bombings in Sweden and acknowledged “public reports” that the group has tried to expand into the U.S.

“We've seen what RIM-trained terrorists can do in Europe, and we want to make sure they not able, or any terrorist group, is not able to accomplish something similar here in the United States,” he said.

Sales's team targeted the movement and three senior leaders individually, one of whom, Stanislav Vorobyev, was quoted publicly discussing their involvement in the Ukraine offensive. "We are aware of public reports that RIM was among the forces that fought in Ukraine on behalf of the pro-separatist forces," he told reporters. "The United States supports the sovereignty and territorial integrity of Ukraine. That is why this administration has provided unprecedented levels of support to our partners in Kyiv as they defend themselves against Russian aggression, including the provision of lethal assistance."

The designation will trigger asset freezes and help border security officials identify and prevent members from entering the United States.

“I can tell you that, as a general matter, any foreign terrorist group that seeks to make common cause with Americans is a grave concern to the United States, grave concern to the State Department, and we will not hesitate to aggressively use our authorities to counter such groups,” Sales said.

The organization is headquartered in St. Petersburg. Sales declined to assert explicitly that RIM is connected to Putin, but he said that the Russian government needs to crack down on the terrorist group.

“As for RIM and its relationship to the Russian government, we call on all partners, our allies in other countries around the world, to take actions commensurate with what we have taken today,” he said. "We are not shy at all in our call for other countries, Russia included, to take decisive action to counter this threat to international security.”