Scotland yard said a cordon was used because missiles were being thrown at officers .
苏格兰场说使用警戒线是因为一直有投掷物扔向警察。
Government troops , tanks and armoured cars are enforcing a forbidding cordon around the desert circuit .
政府的军队、坦克和装甲车正围绕着沙漠赛道组织警戒线。
Armed police moved the onlookers beyond a cordon as paramilitary troops moved in on the building .
部队向建筑物靠近，武警则要求旁观者移到警戒线外。
The violent attempts to break through the police cordon were led by male youths , many from anarchist groups but many ordinary russians were refusing to leave the site of the protest too .
It has used the pretext of an alleged terrorist threat to impose a restrictive security cordon on the city and curtail visas even for harmless businessmen .
