Putin's nuclear alert over NATO leaders' 'aggressive statements'

President Vladimir Putin has ordered Russia's nuclear deterrence forces on high alert. Putin cited 'aggressive statements' by NATO leaders & sanctions against Moscow as reasons behind the decision. Putin's order implies that Russian nuclear forces have been put on high alert, ready for combat duty. Stiff resistance, reports say Russian forces may have been caught off-guard by Ukrainian fighters' pushback. Speaking to CNN, NATO chief Jens Stoltenberg slammed Putin's 'irresponsible' nuclear rhetoric. Top US officials reportedly dubbed Putin's announcement as an 'unacceptable escalation'. Watch the full video for more.