The U.S. Embassy in Kyiv said it has received warning of a potentially significant Russian air attack on Wednesday and would be closed as a precaution.
In a statement, the embassy also instructed employees to shelter in place and also recommended that U.S. citizens in Kyiv be prepared to immediately shelter in the event of an air alert.
The warning was unusual for its specificity as Russian air attacks have become a common, near-daily occurrence in Ukraine.
But it comes one day after Moscow said U.S.-made longer range missiles had been used in a Ukrainian attack that struck a weapons warehouse in the Bryansk region after U.S. President Joe Biden authorized their use.
Russian President Vladimir Putin said in September that if Western countries allow Ukraine to strike deep inside Russia with their longer-rage weapons, "it will mean that NATO countries, the U.S., European countries are at war with Russia."
