China has deployed surface-to-air missile batteries near its main Beijing Olympic venues as an apparent defence against airborne terror attacks on the Games.An AFP reporter saw a pair of missile batteries in clear view under camouflage netting in a grassy area in northern Beijing about one km south ofthe new built National Stadium.The stadium, known as the ‘Bird's Nest’ for its interlacing steel beams, will host the opening and closing ceremonies and other major events during theAugust 8-24 Olympics.China has embarked on a wide-ranging security crackdown ahead of the Games. It has repeatedly warned that it faces the threat of terror attacks on the Olympics,particularly from ‘separatists’ in its far-western Xinjiang region, which is predominantly Muslim.Recent reports in state press said the missiles deployed were of the Red Flag 7 variety. The grassy area, which was protected by a more than two-metre-high(six-foot) security fence, also featured a radar apparatus set-up. The missiles batteries were pointed north in the direction of the stadium.In recent months China has announced it has broken up four separate ‘terrorist’ calls from Xinjiang, two of which planned Olympic attacks. It also has dramaticallytightened airline security after saying that a hijack attempt by a Xinjiang ‘terrorist’ had been foiled in March. It has provided no public evidence ofthe plots.Critics have accused Beijing of exaggerating or fabricating the terror threat to provide an excuse to crack down on any dissent that could embarrass Chinaduring its time in the Olympic spotlight.But the US, Britain and Interpol have all issued travel warnings, saying the Games are a potential target for attack.China has also tightened up requirements for the issuing of visas ahead of the Games. US-made Patriot missiles were deployed for security reasons at the2004 Athens Olympics.