The aim of nuclear exercises planned by Russia is to work out the response to any attacks on Russian soil which the West has allowed Ukraine to carry out with the weapons it supplies, senior Russian security official Dmitry Medvedev said on Friday.

Medvedev, a former president who is now deputy chairman of Russia's security council, warned the West that Russia could attack not only Ukraine in response to such attacks.

"Under certain circumstances, the response (to such attacks) will be aimed not only at Kyiv," Medvedev wrote on the Telegram messaging app. "And not just with conventional explosives, but also with a special kind of arms."

(Reporting by Reuters; Editing by Hugh Lawson)