Posted by 
The US Embassy in Ukraine has closed and instructed its employees to shelter after receiving specific information of a "potential significant air attack" today.
The embassy said the measures were taken out of caution.
"The US Embassy recommends US citizens be prepared to immediately shelter in the event an air alert is announced," the embassy said.
READ MORE: Ninth person charged over shooting that left dad with bullet lodged in his head
The embassy is advising any citizens in Ukraine to identify shelter locals prior to an attack, immediately take shelter if an alert is announced and to follow the directions of Ukrainian officials and first responders in the event of an emergency.
They are urged to monitor local media for any updates.
It comes after Russian President Vladimir Putin yesterday updated the country's nuclear doctrine to lower the threshold for the use of nuclear weapons.
The move would allow a potential nuclear response to any attack on Russia by nations supported by a nuclear power.
– Reported with Associated Press
