NATO head Jens Stoltenberg said Tuesday the "morally totally unacceptable" bombardment of the Syrian city of Aleppo broke international law, while urging Russia to take genuine steps to restore a ceasefire.

"The appalling attacks on Aleppo have shaken all of us, and the violence and the attacks we have seen, also on an aid convoy, is morally totally unacceptable and is a blatant violation of international law," Stoltenberg told a news conference in Bratislava.