Russian officials on Thursday slammed a new round of U.S. sanctions that the Trump administration levied to punish President Vladimir Putin's government for using a chemical weapon against an ex-spy in Britain, saying the measures violate international law.

"In our view, these and earlier restrictions are absolutely unlawful and don't conform to international law," Kremlin spokesman Dmitry Peskov said.

He added that the sanctions are not “constructive” toward the U.S.-Russia relationship.

Peskov also reiterated Russian denials that Moscow had anything to do with the nerve-agent poisoning of former double agent Sergei Skripal and his daughter in the English city of Salisbury in March.

“There can't be any talk about Russia having any relation to the use of chemical weapons,” he said.

On Wednesday, NBC News reported exclusively that Secretary of State Mike Pompeo had signed off on a determination that Russia violated international law by poisoning the Skripals.

That decision that was announced later Wednesday afternoon by State Department spokeswoman Heather Nauert.

Although the U.S. joined European countries in publicly blaming Moscow within days of the attack, the Trump administration had never issued the formal determination that triggers automatic sanctions under a decades-old U.S. law on chemical weapons.

The sanctions are structured in two tranches, laid out in a 1991 law, the Chemical and Biological Weapons and Warfare Elimination Act. An initial, immediate round limits exports and financing but may have limited impact, because it largely overlaps with other restrictions already in place, such as on selling arms to Russia.

A second, more painful round kicks in three months later unless Russia provides "reliable assurances" that it won't use chemical weapons in the future and agrees to "on-site inspections" by the United Nations — conditions unlikely to be met.

Skripal, a former Russian military intelligence officer convicted of spying for Britain, was poisoned with his daughter, Yulia, with the nerve agent Novichok. Both survived.

In late June, two people were exposed to the same nerve agent in an incident that occurred about seven miles away in Amesbury, England. British police believe they cases are linked.

Charlie Rowley, 45, was left critically ill after coming into contact with the liquid.

Rowley last month told NBC News' partner ITV News that the deadly substance was contained in a sealed box of perfume that he had found and given to his girlfriend, who later died.

Moscow has repeatedly denied involvement in either incident.