A Chinese court has ordered the former chief editor of an influential magazine to apologise for challenging an official account of history, as Beijing further tightens limits on freedom of speech.

Hong Zhenkuai cast doubt on the story of the "Five Warriors of Mount Langyashan", who allegedly jumped off a cliff while fighting the Japanese during World War II rather than surrender.

They are touted as patriotic heroes in schoolbooks and propaganda by China's ruling Communist Party as part of its nationalistic narrative.

But Hong pointed out discrepancies in the story in two 2013 articles for his progressive magazine Yanhuang Chunqiu, questioning whether two of the five had jumped at all.

The Beijing Xicheng District People's Court ruled Monday that he had "tarnished their reputation and honour", and hurt the feelings of their two sons, plaintiffs Ge Changsheng and Song Fubao, along with those of the Chinese people as a whole.

The court gave Hong three days to issue a public apology, it said in a statement on its website. It was unclear what penalty he would face should he fail to do so.

The Langyashan soldiers were "a key component of the spirit of the Chinese nation", the court said.

As a Chinese citizen, it added, Hong should have known better than to "diminish their heroic image and spiritual value".

"The defendant had the ability to control the potential damaging consequences that arose out of the articles but did not do so," it said.

"His judgement is clearly faulty and he should bear legal responsibility. The freedom of speech that he advocates is clearly insufficient as a defence against his legal wrongs."

China has imposed ever-tighter restrictions on freedom of speech and the press since Xi Jinping became president in 2013.

The Communist Party tolerates no opposition to its rule and newspapers, websites, and broadcast media are strictly controlled. An army of censors patrols social media and many Western news websites are blocked.

Yanhuang Chunqiu was once one of the country's most outspoken political magazines, known for pieces that challenge official historical narratives, but has faced increased scrutiny and censorship in recent years. In 2015 it was forced to cancel its annual conference under government pressure for the first time in its decades-long history.

The official Xinhua news agency quoted one of the judges in the Five Warriors case as saying: "Free speech is not without boundaries, and it should be protected on the premise that it does not infringe on other people's legal rights."