President Volodymyr Zelenskyy and the US embassy in Kyiv have warned of a significant Russian air attack involving Oreshnik missiles.The alert follows recent Ukrainian drone strikes in Starobilsk, which Moscow claimed caused civilian casualties while Ukraine insisted they hit military units.International intelligence sources suggest that Russia is preparing a combined assault to intimidate Ukraine and escalate the ongoing conflict.Ukraine has pledged a full response to any incoming strikes as officials urge citizens to maintain access to shelters and emergency supplies.