A Chinese cable television service broadcast censored Tiananmen crackdown pictures and messages condemning the ruling Communist party, locals said, in what appeared to be a rare hacking attack.

Viewers in the eastern city of Wenzhou on Friday used social media to post images of television slogans referring to the Communist party as "bandits," and photographs of the bloody 1989 crackdown on pro-democracy protesters in Beijing.

Such images are almost never shown by media in China, where the Communist party censors anti-government messages and references to incidents it deems sensitive such as the Tiananmen crackdown when the army killed hundreds -- by some estimates more than 1,000 -- protesters.

It was not immediately clear who was behind the messages, which appeared on several different channels available through a local cable broadcaster, though Internet users speculated that the provider had been "hacked".

A Wenzhou resident surnamed Gu told AFP that he had turned on his television on Friday evening to be greeted with a photo of a tank on Tiananmen square.

"I found it irritating... it doesn't feel right to vent your opinions by sacrificing others' interests" he said, adding that similar images and anti-communist slogans were broadcast for about four hours.

Another local resident who declined to be named said that his TV had shown a slogan saying: "Bandit Communists you've done too many evil deeds and now you're feeling guilty."

"At the moment some areas of Wenzhou city are receiving unusual broadcasts, technical staff are currently trying to solve this issue, we hope viewers will understand," the Wenzhou branch of China Cable, said on Sina Weibo, a Chinese equivalent of Twitter.

- 'Tank Man' photo broadcast -

Several photos posted on Sina Weibo -- which were later deleted -- showed a TV screen displaying a banner which read "Free Wang Bingzhang", referring to a Chinese pro-democracy activist jailed for life in 2003.

"Communist bandits are the real criminals," a message shown in the corner of one viewer's screen added.

Another photograph showed the channel displaying the iconic "Tank Man" photo from the 1989 crackdown, showing a lone man standing in front of a column of tanks.

Cable viewers also saw a message reading "Friends, don't co-operate with Communist devils," imposed on top of a broadcast of a basketball match.

Subscribers were also shown graphic images showing apparent human rights abuses in the country, such as a protester being squashed under a truck.

China's Communist party does not tolerate organised dissent, and has regularly jailed members of any group which challenges its right to rule the country.

Internet users expressed surprise at the broadcasts, which were said to have ended late Friday, with some speculating that hackers were behind the attack.

Members of the Falun Gong spiritual movement, which has been banned in China since the late 1990s have occasionally been accused of hacking local broadcasters in China to broadcast messages accusing the government of persecution.

"This is a significant event for the television industry," one Sina Weibo user wrote, while another said: "It seems that Wenzhou has been hacked, haha haha."