A Chinese blogger who called on US Secretary of State John Kerry to push for Internet freedom in China has been fired by his employer, he told AFP on Sunday.

Journalist Zhang Jialong was one of four bloggers who met with Kerry in February, where he urged the United States to help "tear down the great Internet firewall".

Beijing tightly censors the Internet, banning websites including Facebook and Twitter with a system labelled the "Great Firewall of China", and ordering domestic Internet firms to delete content that government officials deem "sensitive".

Zhang's employer Tencent dismissed him on Friday for "leaking business secrets and other confidential and sensitive information", he said, calling it a reprisal for his meeting with Kerry.

Zhang said that authorities at Tencent, one of China's best known Internet firms, told him his dismissal was prompted by the meeting, and his posting online of censorship orders issued by China's government.

Directives published by Zhang included an instruction for websites to delete a video by a Taiwanese singer because it briefly showed "a man on an ambulance wearing a Free Tibet scarf".

"Tencent told me they reached the decision after consulting with the government, so it's a political decision," Zhang said, adding that "the situation for online freedom in China is getting worse".

Tencent's Beijing office could not immediately be reached for comment on Sunday.

China has more than 600 million Internet users, the largest online population in the world.

Its ruling party has long been engaged in a "cat and mouse" game with Internet users, tightening restrictions in periodic crackdowns before new forums emerge to challenge restraints.

The rising popularity of microblogs in recent years has triggered a government-backed campaign to assert greater control over social media.

China's Supreme Court last year said Internet users could face three years in jail if "slanderous" information spread online was viewed more than 5,000 times or forwarded more than 500 times.

Hundreds have been detained under the regulation, according to rights groups.