Russia's Oreshnik Missile Threat Sparks Warning
Putin orders military retaliation after drone strike in Luhansk.
Russia has used Oreshnik missile twice, which is hard to intercept.
UK, France, Germany call Oreshnik use 'escalatory and unacceptable.'. Zelenskyy urges preventive actions over post-attack responses.
Zelenskyy warns Oreshnik use sets global precedent for other aggressors.