A man wearing a mask with words "Silent" holds a banner reading: "Let's chase our dreams together, go Southern Weekly newspaper" during a protest outside the headquarters of the newspaper in Guangzhou, on Jan. 7, 2013. (Wu Wei/AP)

Hundreds of supporters of the reform-minded Guangdong newspaper Southern Weekly staged a rare public protest against state censorship outside the paper’s offices Monday, while prominent business tycoons, opinion makers and film stars used their microblogging accounts to demand greater press freedom in China.

Meanwhile, several of the newspaper’s editors and reporters said they were going on strike, which would be the first such action by journalists against official press restrictions in more than two decades.

“This is actually something pretty amazing,” said Hung Huang, a publisher, writer and blogger. “It’s the first time the media is protesting against censorship. This is the first time they took action and said, ‘We’re not going to take this anymore.’ . . . Somehow, this was the straw that broke the camel’s back.”

Cheng Yizhong, a television executive who is a founder and former chief editor of the Southern Metropolis Daily newspaper, called the protests “an explosion that was a long time coming, and with good timing.” He added, “This could be an opportunity to push forward freedom of speech.”

The highly unusual protests sprang from what is being called “the New Year’s Day incident,” in which Southern Weekly’s journalists say their front-page New Year’s message to readers — expressing a “dream” for a constitutional government in China — was substantially rewritten and watered down, without the knowledge or consent of the editors, by Guangdong province’s top Communist Party propaganda official, Tuo Zhen.

Tuo has not spoken about his role in rewriting the piece and could not be reached for comment. Several journalists and media executives said that even under China’s tight, long-standing control of the print media, it would be far out of the ordinary for a propaganda official to so blatantly interfere in the editorial process without telling top editors.

The incident grew more confusing Sunday when a statement appeared at 9:20 p.m. on the Southern Weekly’s Sina Weibo account, the Chinese version of Twitter. The post said the New Year’s message published Jan. 2 was written by the paper’s management team, and it denied the online reports that the message had been rewritten.

About an hour later, angry Southern Weekly editors and staff members used a separate microblogging account, for the paper’s economic news sections, to charge that Southern Weekly’s official Sina Weibo account had been forcibly confiscated by the government and that the statement posted on it was untrue. Dozens of Southern Weekly editors and staff members later signed an online statement saying the paper had been forced to give up the password to the official account.

An estimated 400 people heeded an online call for protests Monday, according to witnesses and online reports . People showed up holding roses and white and yellow chrysanthemums — the traditional flower of mourning in China — and some wore masks covering their mouths. Others held handwritten signs calling for freedom of speech.

“We laid flowers at the gate to Southern Weekly,” said Song Bingyi, a protester. “But once we put down the flowers, plainclothes police came to confiscate them all.”

“I wore a mask to express my anger at being ‘shut up,’ not because I was afraid,” said Ran Xiang, a protester who said she used her weibo account to persuade others to show up at the protest with flowers. She said she brought chrysanthemums because “I hope to pay tribute to Southern Weekly, which is dying.”

The protests spread online, too, with an increasing number of journalists, students, bloggers and public personalities taking to their microblogging accounts to express support for Southern Weekly and call for an end to censorship. The microblogging sites have become an alternative, independent source of information that the Communist Party is trying desperately to rein in.

Among those advocates were the Shanghai race car driver and popular blogger Han Han; well-known actresses Chen Shu, Li Bingbing and Yao Chen, who has more than 31 million followers; actor Chen Kun, with more than 26 million followers; real estate tycoon Ren Zhiqiang; and Zhang Xin, chief executive of Soho China, Beijing’s largest commercial real estate developer, and her husband, Pan Shiyi, the Soho chairman.

Those speaking out on weibo have said that “the New Year’s Day incident” is getting widespread publicity, despite increasingly frantic-sounding edicts from the central government’s propaganda authorities prohibiting the official media from publishing any information about the event. Censors have banned several terms on weibo, including Southern Weekly’s Chinese name and even the word “lump,” which in Chinese is Tuo, similar to the name of the Guangdong propaganda chief at the center of the storm.

Wang Juan and Liu Liu in Beijing contributed to this report.