The Biden administration unveiled sanctions Tuesday against seven senior Russian officials over the poisoning and detention of Alexei Navalny, the most prominent domestic critic of Russian President Vladimir Putin.

Senior administration officials told reporters on Tuesday that the US intelligence community had concluded with “high confidence” that officers of Russia’s Federal Security Service, known as the FSB, poisoned Navalny with the nerve agent Novichok. The use of Novichok agents is barred in warfare under the Chemical Weapons Convention of 1997, of which Russia is a signatory. Navalny is not the first Russian dissident to be poisoned with Novichok, a class of nerve agents first developed by the Soviet Union during the Cold War.

“Russian officials have targeted Mr. Navalny for his activism and efforts to reveal uncomfortable truths about Russian officials’ corruption,” an administration official said. “We’re exercising our authorities to send a clear signal that Russia’s use of chemical weapons and violation of its international human rights commitments have severe consequences.”

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The officials reiterated Biden’s demand that Navalny be released from prison, saying his arrest and detention occurred on “politically motivated grounds.” Navalny was accused of repeatedly violating the terms of his 2014 parole by not reporting to authorities in person, and this included while he was receiving treatment abroad after his poisoning.

Europe’s top human-rights court concluded that his 2014 conviction was “unlawful and arbitrary” and “politically motivated.”

The administration also announced new export restrictions on 14 entities tied to production of chemical and biological weapons in Russia.

The sanctions, which were coordinated with similar actions from the European Union against Russian officials, mark the Biden administration’s first such action against Moscow. The move also represents a departure from President Donald Trump, whose administration barely acknowledged the poisoning of Navalny and did not impose any penalties over it.

“The US is neither seeking to reset our relations with Russia, nor are we seeking to escalate,” one official said. “We believe that the US and our partners must be clear and impose costs when Russian behavior crosses boundaries that are respected by responsible nations. And we believe that there should be guardrails on how these adversarial aspects of our relationship play out.”

Navalny was poisoned in August while in Siberia. He was eventually transferred to Germany for treatment and stayed there for several months. After returning to Moscow in January, Navalny was arrested over the accusations that he violated parole and was subsequently sentenced to 3 1/2 years imprisonment.

The anti-corruption campaigner’s detention led to mass protests in Russia, prompting a violent response from authorities and thousands of arrests.

This report was written by John Haltiwanger and originally published on Insider.