BEIJING: China has threatened to close down the internet news services of Sina Corp , that also owns the country's biggest microblogging site, if it fails to improve censorship of illegal content in the wake of "massive" numbers of public complaints against it.The internet regulator Cyberspace Administration of China (CAC) summoned leaders of Sina Corp, that owns the Chinese equivalent of Twitter called Sina Weibo , to a meeting late yesterday.The meeting was held over "massive numbers of public complaints about its law violations", state-run Xinhua news agency reported today.Since the beginning of the year, the administration has received 6,038 complaints about Sina, more than any other web portal.It said the reports indicated that "Sina has spread illegal information related to rumours, violence and terrorism, pornography, swindling, advocation of heresies and has distorted news facts, violated morality and engaged in media hype," the report said.Sina has also published some false news because of hurry and its censorship of user accounts has been poor, undermining online order and damaging public interests, the CAC added.The government has asked Sina to correct these oversights and strengthen internal management.If Sina fails to meet these requirements, the CAC will "seriously" punish the firm, with possible measures including a complete shut down of its Internet news services.Sina's leaders promised they will intensify censorship and publish more information with "positive energy", the Xinhua report said.Sina Weibo pioneered in social media in China whose online population touched 648 million last year.The expansion of the online population has resulted in the emergence of social media in China which in the past few years have posed a direct challenge to the monopoly of the official media in the country.The microblog media like Sina Weibo, akin to Twitter in China, is used by over 300 million Chinese, prompting the government to bring about detailed rules to regulate the content.