Kyiv, Ukraine - The US has closed its embassy in Kyiv amid concerns over a potential Russian attack on the Ukrainian capital.

The embassy said in an X post on Wednesday it "has received specific information of a potential significant air attack on November 20."

"Out of an abundance of caution, the Embassy will be closed, and Embassy employees are being instructed to shelter in place," the message said.

US citizens in Kyiv were advised to "be prepared to immediately shelter in the event an air alert is announced."

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Greece, Hungary, Italy, and Spain followed suit, announcing the closures of their diplomatic premises in the capital – much to Ukraine's irritation. Its foreign ministry urged Western allies not to fuel what it called an "information and psychological attack" orchestrated through "fake" Russian messages.

The warning comes a day after Kyiv marked the 1,000th day since the Russia launched its full-scale invasion in February 2022, and as the Biden administration announced Ukraine would be allowed to use US-supplied ATACMS missiles against targets inside Russian territory. Ukraine promptly took advantage of the decision on Tuesday, launching several strikes on the Bryansk region.

Russia has said it views the move as an escalation and an entanglement of the US and other Western countries in the war, making them direct participants. Vladimir Putin also signed a decree that enables Moscow to use nuclear weapons against non-nuclear states if they are supported by nuclear powers.

The US embassy regularly issues warnings of major air strikes, including in March and August this year, but the closure represents an exceptional measure.