The Standing Committee of the National People's Congress approved a resolution that makes it a criminal offence to disrupt computer networks or to break into networks for national affairs, defence or high technology.

The resolution, which it says was drafted to promote the healthy development of the Internet and protect national security, also states that it is a crime to use the Internet to spread rumours, promote religious cults, hurt national unity or undermine the Government.

It is also a crime to use the Internet to commit theft or fraud as well as to make slanderous or insulting remarks.

"The resolution will play a positive role in protecting the rights of citizens and corporations on the network," NPC Chairman Li Peng was quoted by China Daily as saying.

Others in the industry welcomed at least some of the provisions of the resolution, which has the force of law.

"It's very good news," said a spokesman for Sohu.com, the Internet portal based in Beijing. "We have to fight hackers."

The NPC's resolution came shortly after the State Council and the Ministry of Information Industry announced regulations tightening surveillance of the Internet.

"These are meant as a supplement to the Internet regulations approved by the State Council," said Philip Qu, a lawyer at Transasia, a Chinese law firm in Beijing.

Mr Qu said since 1977 there had been legislation on the books covering public security and the Internet but that a number of cases had shown the wording was too vague.

China has already jailed - and later released - one Shanghai resident on charges of using the Internet to subvert the state. That case, which involved Lin Hai, who had an online employment service, gained world attention when he stood accused of sending information to a dissident organisation over the Internet.

The use of the criminal law to combat the spreading of computer viruses would be a step forward but might prove difficult to enforce, according to Mr Qu.

"We will have to see technical details on this," said Mr Qu. "This will be a great challenge for the police."

The resolution also states that it is illegal to delete or alter another person's electronic mail.

This probably stems from a case involving a university student in Beijing who used another student's e-mail to try to gain admission to an American university.