BERLIN: German Foreign Minister Frank-Walter Steinmeier has called for a temporary no-fly zone for military aircraft in Syria of up to seven days following the bombing of an aid convoy near Aleppo.

"The situation in Syria is now on a knife edge," Steinmeier said according to a statement tweeted by the Foreign Ministry in Berlin Thursday.

"If the ceasefire is to stand any chance (of succeeding), the only path is a temporary, but complete ban of all military aircraft movement in Syria - for at least three days, better would be seven days," Steinmeier said.

U.S. Secretary of State John Kerry demanded Wednesday that Russia and the Syrian government  immediately halt flights over Syrian battle zones, in what he called a last chance to salvage a collapsing ceasefire.