Chinese bloggers and celebrities along with foreign media campaigners threw their support behind journalists at a newspaper enmeshed in a censorship row on Tuesday, after a rare protest for press freedom.

The widespread backing came after hundreds demonstrated at the Guangzhou headquarters of the popular liberal newspaper Southern Weekly, after an article urging greater respect of constitutional rights was censored by an official.

Wang Keqin, an investigative reporter on another newspaper, posted Tuesday on China's Twitter-like Weibo service: "A black hand closes heavy, black curtain, blocking brightness and fresh air as there is no weekend any more in the south."

The paper's Chinese name translates as Southern Weekend but it is widely known as Southern Weekly in English.

Yao Chen, an actress who has 32 million followers on her Weibo account, earlier posted the paper's logo and quoted Russian dissident Alexandr Solzhenitsyn: "One word of truth shall outweigh the whole world".

Fellow actor Chen Kun, who has 27 million followers, replied: "I am not that deep, and don't play with words, I support the friends at Southern Weekly".

The row erupted after censors Thursday blocked a New Year message in the paper, calling for the realisation of a "dream of constitutionalism in China" to protect citizens' rights, and replaced it with a weaker article, according to journalists.

The dispute over Southern Weekly comes amid pledges of change from the new leadership, headed by president-in-waiting Xi Jinping, which has promised a more open style of governance since the Communist Party congress in November.

Chinese media outlets are subject to directives from government propaganda departments, which often suppress news seen as negative by the ruling Communist Party, but some publications take a more critical stance.

Police allowed Monday's demonstration, which mainly included young people carrying posters and scattering chrysanthemums, a flower used at funerals in China which has become the protesters' symbol for the loss of press freedom.

The international media freedom group Reporters Without Borders praised the protestors' "show of courage" and called for the original article to be published.

"This act of censorship is indicative of the government's habitual contempt for media freedom, although it is guaranteed by the Chinese constitution," its secretary general Christophe Deloire said in a statement.

Pictures of more demonstrations in Guangzhou, although on a smaller scale, appeared on Weibo Tuesday, with the posters saying that was when they were taken.

The gatherings followed an open letter from the newspaper's staff which called for the resignation of provincial propaganda official Tuo Zhen, who was said to have removed the New Year message and replaced it with a weaker article.

The paper had had 1,034 articles changed or withdrawn last year, the editors said in a later message.

Over the weekend a letter signed by scores of prominent academics from across China emerged calling for the immediate removal of Tuo and for greater press freedom.

The popular blogger Han Han, named by Time magazine as one of the world's 100 most influential people in 2010, lamented the pressure that journalists faced.

"It empowers the weak and encourages the pessimists to keep going. So when it is weak and pessimistic, I hope we can give it some small strength and accompany it to keep it going," he wrote, referring to the paper.

Li Chengpeng, who has 6.5 million followers on Weibo, wrote: "We don't need tall buildings... the world's second largest GDP... aircraft carriers, but we need a newspaper that speaks the truth.

He continued: "All the major countries that command respect in the world have a newspaper that is permitted to speak the truth."

But a commentary in the English-language Global Times, which is close to the ruling party, on Tuesday said authorities would not allow radical changes in media policy.

"The country is unlikely to have the 'absolutely free media' that is dreamed of by those activists," it said. "The Southern Weekly issue will not be concluded with a surprise ending."

In an unusual move, the major web major portals carrying the Chinese language version of the article -- Sina, Sohu, Tencent and Netease -- posted disclaimers in an apparent effort to distance themselves from it.

Re-publishing the Global Times article "does not mean that our website agrees with its opinion or verifies what it describes", the message on Sina said.