Russia began exercises to increase the readiness of its tactical nuclear weapons in its southern defence district, the Defence Ministry said on Tuesday, in what is widely seen as a further threat by Russian President Vladimir Putin. Iskander and Kinzhal missiles, tactical weapons that can be equipped with nuclear warheads, are also involved in the drill that was announced earlier this month. These are weapons that can be used selectively against enemy troops and other military targets. They are generally less powerful than the strategic nuclear intercontinental missiles developed mainly as a d…