China on Wednesday executed a street food vendor who drew widespread sympathy after fatally stabbing two "heavy-handed" security officials, provoking outraged webusers to denounce his death penalty as unjust.

China's Supreme Court upheld a death sentence against Xia Junfeng, who murdered two officials after a dispute over his streetside stall in 2009, the Shenyang Intermediate People's court in northeast China said in a verified social media account.

Xia had appealed his sentence on the grounds he killed the two officers in self-defence when they savagely attacked him and others in the city of Shenyang as he barbecued food on the street.

Xia's case drew widespread sympathy amid regular reports of abuses by China's quasi-police city management officials.

The officials, known as chengguan, "have earned a reputation for brutality and impunity... They are now synonymous for many Chinese citizens with physical violence, illegal detention, and theft," a spokeswoman for advocacy group Human Rights Watch said last year.

Hundreds of people rioted in southwest China in 2011 after chengguan reportedly beat a disabled street vendor to death, while the alleged murder of a street vendor in southern China in July provoked a nationwide outcry.

Xia's death sentence was the most discussed topic on Sina Weibo, a Chinese equivalent of Twitter, on Wednesday, where many expressed sympathy for him and called the verdict unjust.

"This was a normal act of self-defence, how can you give the death penalty?" commentator Wei Zhuang wrote.

"This is a father who killed to retain his dignity... at the time (of the murders) shouldn't it be the street, the city and the country who feel guilty?" author Li Chengpeng wrote.

Others questioned the equality of China's legal system, referring ot the high-profile case of Gu Kailai, the wife of former top-ranked politician Bo Xilai, who was sentenced to a suspended death sentence -- usually commuted to life in prison -- last year for the murder of a British businessman.

"Gu Kailai didn't get death sentence for killing. Why did Xia Junfeng get the death sentence for self defence," one Sina Weibo user wrote.

One of Xia's lawyers, Chen Youxi, wrote on Sina Weibo that the court invited Xia's wife to meet her husband ahead of the execution.

"After two and a half years of struggle, we are finally powerless," he added.

Xia's family were reportedly ordered to pay the victims 650,000 yuan ($106,000) in compensation, and were raising money by selling paintings by Xia's son.

China has halved its number of executions since 2007, when its high court began reviewing death row cases, but still puts around 4,000 people to death every year, US campaign group the Dui Hua Foundation estimates.