Russia's President Vladimir Putin on Saturday ordered the start of strategic nuclear exercises involving launches of ballistic missiles, the RIA news agency cited the Kremlin as saying, Reuters reported.

"Yes," Kremlin spokesperson Dmitry Peskov was quoted as saying when asked if the drills had begun.

Separately, Belarusian President Alexander Lukashenko, a close ally of Putin, took part in military exercises alongside Putin from a situation centre in the Kremlin, Belarusian state media reported.