The Syrians have purchased the most advanced ground-to-air missiles from the Russians, considered the cutting edge in aircraft interception technology, said a senior Israeli military source. According to one estimate, the Syrians have more than 200 anti-aircraft batteries of different types. The Institute for National Security Studies recently issued a memo on the strengthening of the Syrian army. Researcher Yiftah Shapir writes that the anti-aircraft deals between Syria and Russia include the purchase of SA-24 missile systems, an armored vehicle which carries four Igla-S missiles - among the most advanced shoulder-fired missiles on the market. In addition, the Syrians purchased 36 to 50 Pantsir S-1 (SA-22) systems that combine missiles and shells. It is installed on a high-mobility vehicle and has a launcher of 12 missiles.