RUTHFULLY YOURS

BUENOS AIRES—President Cristina Kirchner , under pressure here over the case of a dead Argentine prosecutor, courted new controversy on a state visit to China on Wednesday when she mocked Chinese accents.

Mrs. Kirchner, who is in China trying to drum up investment in infrastructure projects, sent out a tweet in which she swapped L’s for R’s in the Spanish words “petróleo and arroz”—petroleum and rice—to caricature a Chinese accent in Spanish.

“Vinieron sólo por el aloz y el petlóleo?” (They came just for rice and oil?), she tweeted rhetorically, referring to hundreds of people at an event where she was speaking in Beijing.

At a daily press briefing on Thursday, Chinese Foreign Ministry spokesman Hong Lei declined to comment on Mrs. Kirchner’s tweet.

However, the news was picked up in Chinese-language media—primarily by Hong Kong and Taiwanese news outlets—prompting criticism on social media platforms.

“It’s too bad your vision is so narrow, but it’s also because you are the president of a trifling country like Argentina—that’s why you’d say these kinds of things,” wrote one Weibo user.

“One day, Chinese will be the world’s language. I believe that day will come sooner or later,” wrote another microblogger.

In official channels and in mainland media, the visit appeared to be going well. The Communist Party’s flagship newspaper People’s Daily ran a front-page photograph of Mrs. Kirchner shaking hands with a smiling Mr. Xi, under a headline declaring both countries’ mutual agreement to deepen their strategic partnership. Similar images and headlines were prominently displayed on the official Xinhua News Agency website and that of state broadcaster China Central Television.

In Argentina, humor highlighting differences in race in culture are commonly employed. Still, more than 41,000 people in Argentina reacted to Mrs. Kirchner’s tweet, most of them by posting comments critical of it, according to www.t-bee.tv, which monitors social networks.

“I feel shame for my country and for some of those that inhabit it,” Twitter user @liturgia16 wrote.

Chin Chau, a mobile phone salesman in Buenos Aires, said in an interview: “I’ve lived here for 55 years and I feel a part of this country. Cristina’s joke was not funny. It shows a lack of respect for Chinese people.”

Mrs. Kirchner immediately followed her joke with another tweet. “Sorry,” she said, “But you know what, the only way you can digest so much excess ridiculousness and absurdity is with humor. If not, things become very, very toxic.”

That tweet appeared to be a reference to the political climate in Argentina, where the circumstances surrounding the mysterious death of a prosecutor have riveted the nation and fed speculation that he was assassinated.

The prosecutor, Alberto Nisman, was found dead at his apartment on Jan. 18, a day before he was to set to testify in Congress that Mrs. Kirchner had conspired with Iran to sabotage his probe into a 1994 terrorist attack that killed 85 people.

Mrs. Kirchner’s response to Mr. Nisman’s death has bewildered many in Argentina. Initially, she indicated he had committed suicide. Days later, she said she was convinced he hadn’t.

More recently, it has been Mrs. Kirchner’s refusal to address the issue in public that has befuddled the public.

On Jan. 30, while the nation’s attention was still focused on Mr. Nisman’s death and his funeral the previous day, Mrs. Kirchner gave an hourlong speech about the economy but didn’t mention Mr. Nisman.

The president’s handling of the case has angered many in this country, where 70% of the population thinks Mr. Nisman was murdered, according to a poll by Ipsos. Almost 60% of Argentines believe Mr. Nisman’s accusations against the president are true, according to a survey by Management & Fit.

With the economy mired in recession and double-digit inflation, Mrs. Kirchner’s approval ratings are stuck at around 26%, according to Management & Fit.

In other tweets, Mrs. Kirchner touted the joint signing of a batch of agreements, including collaboration on nuclear technology and oil and gas partnerships.

But even that news seems likely to be overshadowed by the political crisis surrounding Mr. Nisman’s death. A federal appeals court on Wednesday designated a judge, Daniel Rafecas, to evaluate Mr. Nisman’s allegations against the president. In addition, a prosecutor here is probing his death.

— Alberto Messer in Buenos Aires and Te-Ping Chen in Beijing contributed to this article.