Israel is closely watching developments in Syria, Prime Minister Benjamin Netanyahu said on Sunday.

"We are constantly watching events in Syria. We are determined to defend the vital interests of Israel and to maintain the achievements of war," Netanyahu said, visiting new military recruits at a base in central Israel. Insurgents swept into the Syrian city of Aleppo, east of Idlib province, on Friday night, forcing the army to redeploy in the biggest challenge to President Bashar al-Assad in years.