Authorities in central China released a 12-year-old boy who stabbed his mother to death.
A boy aged 13 from eastern China's Jiangsu province who this month admitted killing his mother when she tried to discipline him was released after spending a day in custody, relatives said.
This came three months after two boys - one aged 13 and the other 12 - admitted killing their parents in two separate incidents in central Hunan province.
None was held responsible for their actions as the boys were not yet 14, the age of criminal responsibility under Chinese law.
The cases intensified public concern that there was a trend towards younger juveniles committing crimes, a problem that was recognised by researchers, the judiciary and legislators.
Professor Song Yinghui, a criminal law expert from Beijing Normal University who has spent decades researching juvenile crime in China, said the number of younger minors breaking the law in recent years had increased.
"Most juveniles who caused serious social damage used to be between 15 and 17, but now many aged between 11 and 13 are also doing so," he said.
Beijing No 1 Intermediate People's Court drew similar conclusions in 2017.
"Judging from juvenile crimes in the past eight years, one obvious trend is the offenders' age has declined," it said in a report on hearings between June 2009 and June 2017.
About 15 per cent of the juveniles involved in the 245 criminal cases heard by the court during the period were between 14 and 16, ages at which defendants can held responsible only for serious offences such as murder and rape.
Those between 16 and 18 can be held responsible for all offences, according to Chinese law.
Song urged the police to establish a national juvenile crimes database and use it to draw a clearer picture of offenders, especially those under 14 who had been suspected of serious offences but did not appear before a court.
Pi Yijun, head of the juvenile delinquency research centre affiliated with China University of Political Science and Law, said that while China did not compile national figures, based on an increased number of media reports it appeared the frequency of murders committed by juveniles was increasing.
"It's undisputed that crimes by children and youths are getting more cruel, for example, killing parents," he said.
In Dazhu county, Sichuan province, a 13-year-old boy confessed to killing his mother in December 2017 after a quarrel.
Local media reported that he decapitated her and shared video footage of the killing on WeChat. The case became public several days later when a classmate of the boy showed the clip to a parent.
The boy was detained by police and then released.
Pi said he believed one reason for such violent behaviour among the young was that China's education system focused too much on hate instead of love.
"We do not have education about love. We believe this is something from and of the West. Instead, we have plenty of violent heroes in textbooks for students to learn from.
"For example, [PLA folk hero] Lei Feng, one of whose mottos is 'treat enemies as brutally and mercilessly as bitter winters'," he said.
While this may in part explain the root of many juvenile delinquencies regardless of age, Song said he believed the age of juvenile offenders had fallen because adolescents were physically maturing faster than earlier generations.
They were also exposed to negative factors at an earlier age and in the home, he said.
"For example, kids today are very likely to become addicted to online games which involve violence and pornography, because these games are not classified and can be easily acquired," he said.
Some legislators have proposed lowering the age of criminal responsibility.
At the annual meeting of the National People's Congress, China's legislature, this month, 30 lawmakers submitted a joint proposal to make children as young as 12 legally accountable for the crimes they commit.
The idea won a lot of support from the public if the response on social media was a measure of opinion, but the legal experts are unconvinced."By doing that, we're only putting more young people in prison, not solving the issues that made the crimes happen," Song said.
"Using criminal penalties on a person whose brain is still developing has a negative effect on his mindset and personality when he grows up. Studies have shown that punishing them this way leads to a higher possibility of repeat offences, so society would pay an even higher price," he said.
Pi agreed that there should be more regulation of children's behaviour outside school to stop misdemeanours sliding into delinquency.
"We have very strict school rules throughout the country, but outside the campus, the children are not given enough attention," he said.
The age of criminal responsibility for minors varies around the world. It is 10 in England and Wales, 14 in Germany and Japan, and in 33 states of the US there is no minimum age at all.