"We've noticed certain complaints. We'll pay attention and try our best to make the Games safe and peaceful," he said.
Asked whether foreign athletes will be allowed to demonstrate their political views through non-violence means at the opening ceremony, Liu said the Olympic Charter has made it clear that "no kind of demonstration of political, religious or racial propaganda is permitted in any Olympic sites, venues or areas."
"People participating the Olympic Games, including athletes and coaches, should observe the regulations of the International Olympic Committee," he said.
But the official said Beijing did designate several parks for protests.
"During the Olympics, in order to ensure a smooth traffic, nice environment and good social order, we would like to ask protestors to go to the designated parks," he said, adding it is also a common practice of some countries.
The official declined to answer how much money Beijing has spent on security, saying that while trying to ensure a safe Olympics, the BOCOG will also spend the money in a thrift way.
