BEIJING: In a major boost to Chinese military, Russia has agreed to sell its sophisticated surface to air missile system to China in an over USD 3 billion deal which could strengthen the world's largest army's air defence specially in high-altitude areas like Tibet The S-400 is a new-generation, anti-aircraft weapon system capable of engaging any aerial target as well as cruise and tactical ballistic missiles, with a maximum speed of 4.8 km per second, according to Russian media reports.The system's 40N6 missiles can destroy airborne targets at ranges up to 400 km, state-run China Daily reported. chief executive of the Russian state-run arms trader Rosoboronexport , has confirmed that China has a contract with his company for the purchase of the S-400."I will not disclose the details of the contract, but yes, China has indeed become the first buyer of this sophisticated Russian air defence system. It underlines once again the strategic level of our relations," the report quoted Isaikin as saying.China clinched the deal in September at a cost of more than three billion for the delivery of at least six S-400 battalions, it said.The sophisticated air defence system is capable of firing three types of missiles, creating a layered defence, and can simultaneously engage 36 targets.The system is able to shoot down aircraft and missiles -- ballistic and cruise -- within a range of 400 km, a report in the Diplomat magazine said.The deployment of S-400 system will substantially improve China's air defence capability, Chinese military experts said."The S-400 is definitely one of the top anti-aircraft weapons in the world. It will greatly supplement the People's Liberation Army 's air defence system, which now has some loopholes in long-range, high-altitude defence of airplanes or ballistic missiles," Wang Ya'nan, deputy editor-in-chief of Aerospace Knowledge magazine, told the daily.