Shanghai Television ran footage identifying several of those suspected of throwing bottles at the Japanese consulate and smashing in windows of restaurants thought to be owned by Japanese during the demonstrations, which involved up to 20,000 people.

``I regret my behavior very much,'' said one of the young men detained, identified as Zhang Jianyong of southern Hubei province.

He was accused of climbing onto the roof of a building and throwing stones and bottles at Japanese bars and shops, the Shanghai Daily reported Tuesday.

The reports did not condemn the protests, saying that most participants were peaceful. But they said violence and other forms of ``disturbing social order'' would not be tolerated.

``Regarding the recent anti-Japan protests, we do not approve of the excesses,'' said Foreign Ministry spokesman Qin Gang Tuesday.

Speaking at a regular briefing, he said authorities are working to protect Japanese missions and individuals.

He did not answer questions about the number of protest-related arrests nationwide.

On the television news, several people shown smashing windows of Japanese restaurants near the consulate in Shanghai's Hongqiao district had their heads circled in red.

The same people were later shown in handcuffs, expressing remorse.

Shanghai police allowed the massive protest on April 16, one of many across the country, to proceed despite warnings against unauthorized demonstrations.

But last week the Public Security Ministry warned against organizing any further rallies.

Last weekend, thousands of police and riot troops were stationed near the Japanese embassy in Beijing and the Japanese consulate in Shanghai, apparently to deter any further violence.

Japan's foreign minister, Nobutaka Machimura, said in Tokyo Tuesday that he is not expecting big rallies during the holiday week and that he believes protesters are put off by the stepped-up security.

Of the 42 seized by Shanghai police, 26 were put on ``short-term detention,'' Shanghai Daily said.

Activists had called for more protests during the Labor Day holiday and on May 4, the date of a 1919 student uprising over a treaty that ceded part of China to Japan.

But several of the activists' Web sites have been closed down amid warnings against organizing protests online or through mobile phone text messages. ASSOCIATED PRESS