The US embassy in Kyiv has issued a statement, warning US citizens in Kyiv of a "potentially significant" air attack that may occur at "any time over the next several days."
Shortly afterwards, Russia announced a NOTAM (Notice to Airmen) for the airspace around the Kasputin Yar Test Site, stating that the airspace will be closed for a 22-hour period from 9am on May 12 to 7am on May 13.
The Kapustin Yar Test Site is from where Russia last launched an Oreshnik intermediate-range ballistic missile.
Interestingly, before that same strike, the US embassy in Kyiv issued a similar warning beforehand.
The ORESHNIK proved to be an unstoppable hypersonic missile. No present interceptor technology anywhere in the world is able to stop it.