Shanghai public security authorities have warned that they will not approve an anti-Japan march scheduled for the city centre tomorrow amid apparent concerns about the impact on businesses. 'We haven't received any applications for protests on Saturday, but one thing is for sure: we're not going to give it the green light if there's such a request,' an official with the Shanghai Municipal Public Security Bureau told the South China Morning Post. Any mass protest without government permission was unlawful, he added. Some of the city's mobile phone users yesterday received text messages calling on them to remain calm. 'Shanghai Public Security hereby reasserts: according to law, protests require approval. People should express patriotism orderly, rationally and legally. Express patriotism in a proper manner, obey the law and maintain order self-consciously,' read a message sent to China Mobile subscribers. When contacted, a China Mobile operator said the text message had been sent out to subscribers on local government orders. But the Public Security Bureau denied responsibility. Mainland media reports said protests had also been planned in other cities, including Beijing, Shenyang and Dongguan . Shanghai has so far been untroubled by the violent protests seen in other cities, such as Beijing and Guangzhou, targeting Japanese stores and diplomatic buildings. The municipal government on Wednesday vowed to protect foreign property in the city, where Japanese businesses play a prominent role. The city is home to 20,000 Japanese nationals. On Saturday, three Japanese students were assaulted in a Shanghai restaurant after apparently being targeted due to their nationality. Calls for an anti-Japan protest march in Shanghai this weekend had emerged on several nationalist websites and mobile phone text messages. One posting on the website of the Patriot Alliance reads: 'Who said we are unconcerned? Our blood is boiling with indignation.'