Beijing- China's legislature approved a sweeping national security law on Wednesday to tighten control of the internet and empower the state to take "all necessary measures" to protect its sovereignty.The far-reaching and vaguely worded legislation calls for vigilance and defence against "bad cultural influences", "malignant groups" and "criminal activities under the guise of religion" and warns of interference of foreign powers in internal affairs.It calls for tougher management of the internet, including measures to prevent the spread of "illegal or harmful information"."This would restrain the freedom of online speech even more, stifling critical voices to the government," Beijing-based political commentator Zhang Lifan told dpa.The law adopted by the National People's Congress Standing Committee covers areas including defence, finance, science and technology, culture and religion.It defines national security for the first time as a "condition in which a country's government, sovereignty, unity, territorial integrity, population, economy and society are relatively safe and not subject to internal and external threats".Committee representative Zheng Shuna rejected criticism that the definition was too broad."Any government will stand firm and will not leave any room for disputes, compromises and interferences when it comes to protecting their core interests," she said.'Draconian'The law has drawn widespread criticism from foreign companies, diplomats and human rights groups.Amnesty International called the law "draconian"."The vague list of restrictions in the name of national security will make it impossible for people to know what behaviour is actually prohibited and will allow the authorities to prosecute anyone who essentially crosses their ever-moving line of 'illegal activities'," said Amnesty's China researcher William Nee.Experts said the law would institutionalise existing methods of social control."Frankly speaking, this law has been briefed inside the system for a very long time, and in fact, many of the components that look surprising were already unspoken rules that have now been clarified," said Chu Yin, associate professor at the International Institute for International Relations in Beijing.Foreign diplomats have expressed fears that the law would create "back doors" for spying if government inspectors force technology firms in China to release sensitive information such as source codes.China and the United States have recently blamed each other for cyber attacks on their domestic internets and other online systems.The law does not include details on how it would be enforced.