An AFP reporter on Wednesday saw a pair of missile batteries in clear view under camouflage netting in a grassy area in northern Beijing about one kilometre (half a mile) south of the newly built National Stadium.
The stadium, known as the "Bird's Nest" for its design of interlacing steel beams, will play host to the opening and closing ceremonies and other major events during the August 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 missile batteries were pointed north in the direction of the stadium.
In recent months Chi