Twelve soldiers belonging to Iran's Revolutionary Guard Corps were killed in Sunday's Israeli airstrikes on Damascus's International Airport, the UK-based NGO Syrian Observatory for Human Rights charged on Tuesday.The report said 21 people were killed in total, among them six members of Bashar Assad's regime forces and 15 non-Syrian nationals. Of the 15 non-Syrian nationals, 12 were Iranian forces, the report said. The report further claimed three squadrons of Israeli jets carried out the attack on Syiran positions. IDF fighter jets struck Iranian and Syrian military targets, air defense batteries and Quds Forces positions throughout Syria in the predawn hours of Monday. The military targets belonging to the Quds Force included weapons storage sites, a site at Damascus Airport, an Iranian intelligence site and an Iranian military training camp.According to IDF spokesman Brig.-Gen. Ronen Manelis, the airstrikes were carried out in three waves in response to the Iranian Revolutionary Guard Corps firing a surface-to-surface missile a day earlier toward the Golan Heights, which was intercepted by the Iron Dome missile defense system. The missile fire drew a rare response from Israel, as it carried out daytime strikes on Syrian targets.Prime Minister Benjamin Netanyahu warned Israel will continue "operating against Iran and against the Syrian forces that are abetting the Iranian aggression," he said on Monday. "We will strike anyone who tries to harm us," the prime minister said, reiterating his long-standing claim Israel will not allow for Iranian entrenchment in Syria.Iran's former defense minister, Admiral Ali Shamkhani said on Tuesday that Iran is not threatened by Prime Minister Benjamin Netanyahu and will be working with Syria to fight terror, according to Channel 12.“Cooperation with Syria is essential to eradicate terror,” the senior official said in the report. “Our policies are founded on being good neighbors.”"A good dialogue with our neighboring countries is important in order to deal with the security crisis in the region," Shamkhani continued.Shamkhani's statement comes the same morning as Israel successful tested an Arrow-3 missile interception system, which defends against ballistic missilesIn a related development, The British Royal Air Force will reportedly pull out more than half of its fighter jets operating over Iraq and Syria, following United States President Donald Trump's decision to withdraw US forces from the area, according to the British tabloid the Daily Mail. "This in no way weakens our resolve to carry out missions against ISIS," a senior UK defense official told the paper.Anna Ahronheim contributed to this report.