In a retaliatory move, massive Russian air strikes have killed at least 30 militants in Syria, where a Russian fighter jet was shot down, an official said on Sunday. "A series of high-precision weapon strikes have been delivered in the area controlled by the Jabhat al-Nusra terrorist group, which brought down the Russian Su-25 jet by using a portable anti-aircraft missile system in the Syrian province Idlib," Russia's Defense Ministry said. "According to radio intercepts, more than 30 Jabhat al-Nusra militants were killed," Xinhua quoted the ministry as saying. Earlier on Saturday, the ministry said a pilot survived the fighter jet crash but was later killed in a ground fight with terrorists. The pilot had reported earlier that he ejected by parachute in the area, controlled by Jabhat al-Nusra militants. In May 2017, the guarantors of the Syrian ceasefire - Russia, Iran and Turkey - agreed to set up the Syrian de-escalation zones in Syria, which includes Idlib province.