China has designated three Beijing parks for demonstrations during the Olympics, but has told protesters they must apply five days in advance of any rally.
The Olympics, which open on 8 August, have galvanised critics of China around the world on an array of issues, including treatment of internal dissidents, notably in Tibet, and censorship of the internet.
Protests on the Olympic torch relay's international legs remain one of the year's abiding global images.
China has a 100,000-strong security force on hand to deal with terrorism or anti-government protests during the largest international event Beijing has staged.
Nepal detained 253 protesters, including Tibetan monks and nuns, who tried to stage a silent protest march in front of a Chinese visa office in Kathmandu. Police said the protesters would be freed later on Sunday.
Meanwhile, a youth orchestra of 2,008 international musicians became the first foreign group to play in Tiananmen Square. They performed a medley of classical and modern pieces at the Beijing landmark that is best known to the world for student protests in 1989.
One of the participants, Guam Territorial Band leader Max Ronquillo, said it was a significant message from the Chinese to say that China is now open to the world.
Weather forecasters have predicted thunder and rain in Beijing on the day of the Olympic opening ceremony, and warned that typhoons could disrupt events in other host cities.
Organisers have repeatedly said rain is their biggest worry ahead of the 8 August ceremony, which will feature more than 10,000 performers and a massive fireworks display.
Officials from the Beijing Meteorological Bureau confirmed that bad weather was certain for Friday, although they held out hope that the skies may clear for the evening ceremony.
"Before and immediately after 8 August, we will not see persistent heavy rainfall," said the bureau's deputy director Wang Jianjie. "Specifically on the 8th, the weather in Beijing will be cloudy and overcast, and we will see some rain showers and thunder showers."
As for typhoons, she said two or three were expected to blow in from the Pacific Ocean during the Games period, August 8-24, and they would be tracked and monitored throughout that time.