Israeli Prime Minister Benjamin Netanyahu flew to Moscow on Monday to seek reassurance from Russian President Vladimir Putin about Moscow's military deployment in Syria and to lay out Israel's concerns about the risk of weapons reaching militants on its borders.

With fighter planes included in the rapid Russian buildup, Israel is worried about the threat of fire accidentally being traded with Russian forces, especially since it has carried out air raids against militants in southern Syria and against Lebanese Hezbollah fighters suspected of smuggling arms.

A former strategic adviser to Netanyahu said the Israeli leader would try to work out "ground rules" with Putin about avoiding such clashes.