The Kremlin said on Thursday that the Czech Republic's decision to freeze Russian state-owned properties was illegal and that Moscow may retaliate against what it called a hostile step.

The Czech government said on Wednesday it had frozen Russian state-owned properties on its territory, expanding its sanctions imposed over Moscow's war in Ukraine.

Kremlin spokesman Dmitry Peskov said the Czech move was illegal under international law and that Moscow would study it.

"All of our facilities that may be our property there, with the exception of those that have diplomatic status, are of course now under threat. The situation is now being analyzed in order to somehow minimize the risks," he told reporters in a briefing.

"Such a profoundly anti-Russian position from the Czech authorities is, of course, absolutely bewildering. We categorically reject this position, which is unacceptable."

Prague said it had widened its national sanctions list to include a Russian company controlled by the presidential administration that was in charge of managing Russian assets abroad.