New U.S. sanctions against Russia are “absolutely illegal” under international law, a spokesman for the Kremlin said Thursday after news of the penalties sent the Russian currency plummeting.

The fresh set of sanctions are the result of a just-concluded investigation into Russia’s alleged use of the illegal nerve agent Novichok in an assassination attempt against ex-spy Sergei Skripal and his daughter Yulia Skripal in the United Kingdom. The sanctions are set to take effect at the end of August and come on the heels of President Donald Trump’s much-criticized meeting last month with Russian President Vladimir Putin.

Kremlin spokesman Dmitry Peskov slammed the economic penalties, but maintained that Russian finances are “stable,” according to Reuters. Russia has denied any involvement in the attack against the Skripals.

“Making a linking to these events is for us unacceptable and such restrictions like those passed by the American side earlier… are absolutely illegal and do not correspond to international law,” Peskov said, according to Reuters.

The first round of sanctions will target items related to national security, and hit many items previously banned by other restrictions. A second round of tougher sanctions could be imposed later if Russia fails to meet certain conditions.

Read this next: Kremlin: New US sanctions are ‘absolutely illegal’