The Chinese authorities have put on a show of force in Beijing and Shanghai.
They focused on city centre locations where activists had urged people to gather to show their opposition to government policies on Sunday.
The appeal for people to come onto the streets, for the second week in a row, originated on a website outside China.
The authorities have been censoring Chinese microblogs and internet sites to try to prevent information about the call to protest spreading.
Blowing whistles and using loud-hailers to urge people to move on, the police tried to stop a crowd forming on the edge of Shanghai's main square.
There were more than 100 officers, many more than the week before.
They used large street cleaning vehicles to sweep along the block repeatedly, to help keep people moving.
They tried to stop journalists filming, taking pictures or talking to any of the bystanders.
There was a similar show of force in Beijing where more than 300 officers kept people from approaching the designated protest spot which had been fenced off.
After half an hour they started clearing the area.
A BBC crew was detained after they tried to film what was going on. They were taken to a nearby police station where they were released.
On the internet the call had gone out for people to take part in what were called "strolling protests".
If there were protesters they kept a low profile.
In Shanghai five men were bundled off by police. One had been taking pictures. It was not clear what the others had done wrong.
Those who gathered to watch the commotion appeared puzzled about what was going on.
There was a lot of quiet grumbling about the government but no one was willing to speak out with so many officers, both in uniform, and in plain clothes pushing them around.
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