The U.S. Embassy in Kyiv has issued a warning for staff to shelter in place, citing a “significant air attack” threat from Russia. This follows President Joe Biden’s decision to allow Ukraine to use long-range missiles to target sites within Russia.

“The U.S. Embassy in Kyiv has received specific information about a potential significant air attack on November 20,” read a statement on the embassy’s website. As a precaution, the embassy announced its closure and instructed employees to shelter in place.

The advisory also urged U.S. citizens in Kyiv to remain vigilant, monitor local media, and be prepared to seek shelter immediately in the event of an air alert.

The heightened threat comes shortly after Washington lifted its restriction on Ukraine using U.S.-supplied long-range missiles to strike deep into Russian territory. This move, intended to bolster Ukraine’s defensive capabilities, comes nearly 1,000 days into the conflict.

The Advanced Tactical Missile System (ATACMS), now authorized for Ukrainian use, has a range of 190 miles (300 kilometers) and could potentially target Russian positions previously out of reach. In response, Russia has reportedly relocated many of its fighter jets and bomber aircraft further east, away from the missiles’ range.

The decision also aligns with U.S. efforts to counter the involvement of North Korean troops, who are reportedly reinforcing Russian lines. U.S. officials stated that the missiles would be deployed against both Russian and North Korean forces, particularly in Russia’s Kursk region.

The U.S. government framed this policy shift as a direct message to North Korea, marking its first ground troop deployment in support of Russia since the Korean War.