The US embassy in Kyiv warned Wednesday of a "potential significant air attack" and shuttered its doors, following Russia's vow to respond after Ukraine fired longer-range US missiles at its territory for the first time.
"The US Embassy in Kyiv has received specific information of a potential significant air attack on November 20," it said in a message on its website.
"Out of an abundance of caution, the Embassy will be closed, and Embassy employees are being instructed to shelter in place," it added.
"The US Embassy recommends U.S. citizens be prepared to immediately shelter in the event an air alert is announced."
Russia warned on Tuesday that it would respond after Ukraine fired longer-range US missiles at its territory -- a first in the nearly three-year war.
A senior Ukrainian official told AFP that a strike on Russia's Bryansk region on Tuesday "was carried out by ATACMS missiles" -- a reference to the US-supplied Army Tactical Missile System.
Russian Foreign Minister Sergei Lavrov said the attack showed Western countries wanted to "escalate" the conflict.
"We will be taking this as a qualitatively new phase of the Western war against Russia. And we will react accordingly," Lavrov told a press conference at the G20 summit in Brazil.
Washington this week said it had cleared Ukraine to use ATACMS against military targets inside Russia -- a long-standing Ukrainian request.
