Chinese police have begun to detain and punish people for spreading rumours online, the government said on Tuesday, as authorities intensify efforts to censor content on the Internet.

A university student in southwest China's Yunnan province was detained for disseminating fake information on a local murder, the State Internet Information Office said, while a man in Shanghai was taken into custody for 15 days for posting falsified tax documents online.

Police were also seeking the whereabouts of those responsible for posting false information found on three popular websites, the newly established office said in statement on government websites.

It did not detail what kind of information had been posted.

The moves come after Chinese authorities had vowed to crackdown on rumours and false information on the Internet.

China -- which has the world's largest online population with more than half a billion users -- constantly strives to control the Internet, blocking content it deems politically sensitive as part of a vast censorship system.

But the rise of China's weibos -- microblogs similar to Twitter, which is banned by the communist authorities -- has exposed the difficulty of controlling access to information.

Meanwhile more and more Chinese are turning to weibos to vent their anger over government corruption, scandals and disasters in a country where authorities maintain a tight grip on the media.

Tuesday's statement said that in the latest crackdown an editor at an Internet website had been warned for publishing a microblog entry concerning the recent crash of an air force fighter jet "without confirming the source and facts."

"Authorities will step up efforts to stop rumours and punish individuals and websites spreading rumours," the statement said.