NATO’s top official on Tuesday called on allies to step up arms supplies to the Ukrainians, especially sophisticated air defense systems, a day after Russia rained rocket fire on 19 cities across Ukraine in a marked escalation of its assault on civilians.

As missiles and rockets continued to strike Ukraine, although in smaller numbers than Monday, NATO Secretary-General Jens Stoltenberg said that Moscow’s aerial attacks on civilian targets were "a sign of weakness” and that Ukraine would be better able to deter them if its existing weaponry was expanded.

"These air defense systems are making a difference because many of the incoming missiles were actually shot down by Ukrainian air defense systems provided by NATO allies,” he said.