The French foreign office on Tuesday summoned the Chinese ambassador, Lu Shaye, to express its deep disapproval about Chinese diplomats’ claims that France had left its older citizens to die.

The allegation, and similar attacks, are linked to Chinese “wolf warriors” on social media. The new, assertive brand of diplomacy is favoured not only by younger diplomats but also by the Chinese ministry of foreign affairs. Wolf Warrior is a 2015 action film popular in China.

The controversy follows a series of acerbic anonymous posts on the Paris embassy’s website, ascribed to a Chinese diplomat, culminating in an article saying: “Residents of retirement homes were made to sign certificates of ‘waiver of emergency care’; the nursing staff of the Ehpad abandoned their posts overnight, deserted collectively, leaving their residents to die of hunger and disease.”

The use of the French acronym Ehpad (Établissement d’hébergement pour personnes âgées dépendantes) left no doubt China was referring to France. But the French press say the Chinese claim may refer to an article, directed at Spain, in the Ouest-France newspaper.

Later, the Chinese embassy source writes: “WHO [World Health Organization] has been the subject of a veritable siege on the part of western countries, some even launching ad hominem attacks against its director general, Dr Tedros Adhanom Ghebreyesus. The Taiwanese authorities, supported by more than 80 French parliamentarians in a cosigned statement, even used the word ‘negro’ to attack him. I still do not understand what could have gone through the heads of all these French elected representatives.” No reference to “negro” is made in the parliamentarians’ statement.

The account also denounced western politicians for advocating “herd immunity”, saying they had abandoned their citizens to a viral massacre.

France has worked hard to improve relations with China, which has sent it masks, so had been reluctant to trade insults.

Explaining the summons, the French foreign office said: “Some recent public statements by representatives of the Chinese embassy in France do not conform to the quality of the bilateral relationship between our two countries.”

China has been embroiled in Twitter disputes not only in Europe, but in Khazakstan, Iran, Pakistan and Singapore. It has also argued with the Brazilian education minister over statements that Beijing planned world domination.

In Sri Lanka, the Chinese embassy’s Twitter account has only just been restored after it was shut down for allegedly being inflammatory. The reopened account said: “When westerners publish their opinions, it’s called freedom of speech, no matter how false. When Chinese say something different from them, it’s called a disinformation campaign. Hilarious double standards.”

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The Chinese ambassador to Cyprus, Huang Xingyuan, was also in trouble for saying the world was embarrassed by how quickly China had solved the virus outbreak, and had resorted to “blame shifting and lies”. In another post he wrote: “Sad to see #Boris [Johnson] tested positive and confirmed cases surpassing 100k in US. Hope it’s not the result of herd immunity policy.”

In the Netherlands, the Chinese embassy accused the newspaper Volkskrant of running far-fetched and malicious stories. And in India, the Chinese spokesman tweeted that a call for his country to offer compensation for coronavirus was “ridiculous & eyeball-catching nonsense”.

China’s new assertiveness marks a break not only from traditional diplomacy, but from the country’s advocacy of non-intervention in the affairs of other states.

Although most Chinese embassy channels defend China’s handling of the pandemic, and detail its generosity in supplying protective equipment, they also sometimes promote conspiracy theories about the source of the outbreak. It is part of a new “fighting spirit” demanded of diplomats in a memo last year by the president, Xi Jinping.

The new head of the foreign ministry’s information department, Hua Chunying, last year lamented the lack of that spirit among China’s diplomats and said that in a chaotic world, with deepening rivalries, Beijing had to do more to get its case across.

According to the non-partisan thinktank the German Marshall Fund, Twitter accounts linked to the Chinese embassies, consulates and ambassadors have increased by more than 250% since the start of the Hong Kong anti-government protests in March 2019. From September to December alone, China’s diplomatic corps created more than 40 new accounts, about the total it had had before April 2019.

China says it is no longer taking criticism – such as the daily outpourings on Twitter from Donald Trump – lying down, and is legitimately defending its corner in the same way as the west, or indeed Russia.

Not all Chinese diplomats approve, however, with the ambassador to Washington, Cui Tiankai, saying claims promoted by some official Chinese channels that the US marines planted the virus in China were “crazy”.

In the UK, the Chinese ambassador, Liu Xiaoming, is steering a middle course. He has previously held press conferences to denounce British media criticism of China’s handling of the Hong Kong protests, and the embassy website is full of his letters to the British press, including the Guardian, challenging its stories and denouncing anti-Chinese bias. However, he has not criticised Britain’s response to coronavirus.

The question is whether China is using official accounts to promote conspiracy theories. Yun Sun, a co-director of the Washington-based thinktank the Stimson Centre, testifying before the Canadian parliament, said: “What we have witnessed with Chinese foreign policy is an assiduous attempt to break away from the western discourse and re-establishment of the traditional Chinese model of hegemonic stability.”

She said she had no doubt the conspiracy theories were authorised from the top.