MOSCOW—Russian President Vladimir Putin ordered snap military drills Thursday to test the combat-readiness of troops on the country’s western flank.

The exercises, announced by Defense Minister Sergei Shoigu, come amid heightened tensions with Ukraine. Russia, which is covertly supporting separatists in its neighbor’s east, blamed Ukraine for the deaths of two service members earlier this month in Crimea, which Russia annexed in 2014.

The exercises will test the ability of forces in the south “to deploy promptly self-sufficient forces to localize crisis situations” and for forces in the western and central districts to send support to the southeast, the Defense Ministry said. They will last through the end of the month.

Deputy Defense Minister Anatoly Antonov had been ordered to inform foreign military attachés about the drills, the ministry said.

Mr. Shoigu told a meeting of top military officials that troops in the southern, western and central military districts, the Northern Fleet, aerospace forces and airborne troops were put on full combat alert at 7 a.m. for the drills.