Shanghai police have issued a public notice warning people not to attend protests or use the Internet or cell phones to organize unlawful gatherings — underscoring moves to prevent further anti-Japanese demonstrations in China (search).

Newspapers on Wednesday also reported the arrest of Tang Ye, a company employee accused of disturbing social order by distributing protest plans via the Internet.

The arrest, along with more than a dozen others in recent days, appeared to reinforced the message that anti-Japanese demonstrations (search) such as those held in several Chinese cities in recent weeks would no longer be tolerated.

The often violent protests, including one in Shanghai on April 16 that involved about 20,000 people, have helped plunge relations between Japan (search) and China to their lowest level in more than three decades.

"It is forbidden to engage in unlawful gatherings, demonstrations or protest activities of any kind," said the police notice, which was carried on the front page of newspapers Wednesday.

"It is forbidden to use the Internet or mobile phone messages or other means to organize or incite illegal gatherings, demonstrations or protest activities," it said.

The Communist Party newspaper Liberation Daily said Wednesday: "The public and students must obey the law, not spread rumors or gossip and not participate in any unlawful activities or protests."

In recent weeks thousands of Chinese were allowed to conduct anti-Japanese demonstrations in many major cities, despite warnings against unauthorized protests. In Shanghai and Beijing, protesters vandalized Japanese-related shops and smashed windows at Japanese diplomatic missions.

The protesters were expressing opposition to new Tokyo-approved history textbooks that critics say whitewash Japan's World War II atrocities and to a bid by Japan to join the U.N. Security Council.

Though Beijing has not condemned the protests, it has sought to prevent further unrest on politically sensitive dates such as May 4, the anniversary of a 1919 student uprising over a treaty that ceded part of China to Japan.

On Tuesday, the government said it had arrested 16 people in connection with the protests and briefly detained another 26.

The police notice said authorities were pursuing lawbreakers who damaged public and private property and disturbed social order. It repeated a call for offenders to surrender and for others to inform on them.

Patriots should concentrate on work and studies, it said.

"The public must trust the party and the government's ability to promote the country's long-term interests and correctly handle relations with Japan," it said.