Chinese football has been plagued by allegations of match-fixing and the penalty decision allowed the visiting side from the city of Qingdao to draw the game 3-3 with the home team.

The incident has received wide coverage by China's normally reticent state-run media.

Two years ago there was crowd trouble at another football game in Xian over a similar disputed penalty decision, prompting the government to demand more action to stamp out hooliganism at matches.

Corruption allegations

The clashes began when, three minutes into injury time at the end of the game on Sunday, the referee awarded a penalty kick to visiting team Qingdao Yizhong which allowed the First Division players to level with home side Shaanxi Guoli.

Football hooliganism in China is getting worse

As the final whistle was blown, fans are reported to have pelted players and police with plastic bottles, lighters and other missiles, screaming abuse before setting the stadium seats on fire.

"Shouts of 'Black whistle! Black whistle!' shook the heavens and earth," reported the Xinhua Sports Express. The term of abuse is used to describe corrupt referees in China.

After the police succeeded in evicting the rioters from the stadium, fresh fights broke out in the streets, the paper said.

A police van was torched and four other police cars were overturned, it reported.

Xian police told the news agency AFP that "only a small number of clashes broke out, but the fans damaged several police cars".

Another official said that "no more than 20 people" were arrested.

Reporting freedom

But China's media carried dramatic photos and reports of the rioting.

China, which controls most of the press, usually keeps a tight reign on the media, which shies away from reporting mass unrest.

Correspondents say the episode shows how much more freedom sports editors enjoy than their political colleagues.

Football hooliganism in China has been growing following a wave of allegations about corrupt refereeing. When Shaanxi Guoli fans also rioted in 2000 they were banned from playing home games for the rest of the season.