A Chinese court on Friday declared innocent a man sentenced to death six years ago for a double killing, in a case which highlighted flaws in the country's legal system.

Nian Bin, a former food-stall owner, was convicted of poisoning two children and condemned to die in 2008, and had been held in custody ever since.

His case went through multiple appeals, with lawyers arguing that the evidence against him was insufficient and police had tortured him into confessing, until the high court of Fujian province quashed his conviction Friday and freed him.

Acquittals in China's Communist-controlled court system are extremely rare -- 99.93 percent of defendants were found guilty last year, according to official statistics.

Beijing does not say how many people it executes each year. But independent estimates put the total around 3,000 in 2012, a figure higher than all other countries combined.

The use of force to extract confessions remains widespread in the country, leading to a number of miscarriages of justice.

"None of the evidence presented in the case can be properly verified," the Fujian court said in a microblog post announcing Nian's innocence.

His lawyer Si Weijiang wrote in an online post: "We hope that the reversal of the verdict in this case can allow other unjust verdicts to be overturned.

"His family home has been subject to revenge attacks, his daughter's mental health has suffered, while his wife has waited in pain for six years," he added.

Nian, now 38, told a previous court hearing that police had hung him from a hook and beaten him until he confessed, reports said.

He was first detained by police in 2006, after two children died and four other people fell ill in a family near his home, apparently from consuming rat poison.

The UK-based rights group Amnesty International said in a statement that the quashing of Nian's conviction was "another reminder of the need to immediately end all executions and abolish the death penalty in the country".

"The ever present risk of executing innocent people is just one of many compelling arguments against the death penalty," it added.

China has occasionally exonerated wrongfully executed convicts after others came forward to confess their crimes, or in some cases because the supposed murder victim was later found alive.