KYIV — The US embassy in Kyiv has shuttered fearing an imminent "significant air attack" in Kyiv, according to a statement published on its website.

"Out of an abundance of caution, the embassy will be closed, and embassy employees are being instructed to shelter in place," the statement said, adding that US citizens in Kyiv should also be prepared to shelter.

The warning comes a day after Ukraine reportedly used US-supplied Army Tactical Missile Systems, known as ATACM missiles, to strike Russian territory for the first time after US President Joe Biden reportedly green-lighted the weapons following months of hesitation.

In response, Russia lowered its threshold for a nuclear strike in response to a broader range of conventional attacks on Tuesday.

The Kremlin has long warned that the use of such weapons by Ukraine supplied by its foreign allies would mark a serious escalation in the war.

On Wednesday, South Korea's spy agency also reported that North Korea supplied additional artillery systems to Russia to support its war efforts against Ukraine.

US, South Korean and Ukrainian intelligence have confirmed thousands of North Korean soldiers are currently in the Kursk region, where Ukrainian forces launched a surprise insurgency against Russia earlier this year. – Euronews