TOKYO -- In a fresh sign of the bitter power struggle going on in China, an explosive open letter appeared briefly on a state-sanctioned website calling for President Xi Jinping to resign over economic mismanagement.

The letter was not signed. It was posted by Wujie News in early March, shortly before the National People's Congress, China's parliament, kicked off its annual meeting at the Great Hall of the People in Beijing.

Xi also helms the Chinese Communist Party. The highly unusual public lambasting blamed Xi for China's slowing economy, now the world's second-largest, and called for him to resign from all party and state leadership posts.

It did not start out this way for Xi, who became president a little more than three years ago and launched a sweeping anti-corruption campaign to wide acclaim.

The campaign, however, quickly became a hammer that Xi has wielded against political foes and to consolidate power.

The defiant letter credited Xi's "high pressure" anti-corruption campaign with helping to correct rampant misconduct among party officials.

Chinese President Xi Jinping

But it went on to say the campaign has also led to a "slacking-off phenomenon" at all levels of government, with frightened bureaucrats failing to do their jobs. This has further accelerated the deterioration of China's economy, the missive said.

The letter also said the current aim of the anti-corruption drive is to quench Xi's thirst for power.

The posting was the first criticism released inside China to openly and clearly link the anti-corruption campaign to the worsening economy. It blamed China's current economic woes on Xi, not Premier Li Keqiang.

Li, ranked second in the Communist Party hierarchy, after Xi, was supposed to serve as the economic czar in Xi's administration. But he has ended up with no such authority due to Xi's aggressive consolidation of power.

The letter also pointed out that Xi has abandoned the Communist Party's traditional principle of collective leadership exercised through the Politburo Standing Committee.

The Politburo Standing Committee is the ruling party's top decision-making body. It currently has seven members, including Li and Xi.

There are rumors that insiders worked to get the letter posted on Wujie News. In addition to calling for Xi to resign from all party and state leadership posts, the missive warned Xi to watch out for his and his family's physical well-being.

The letter appeared only briefly before being taken down. Still, it was read by many before disappearing and has made a big splash elsewhere on the Internet. Copies are still making the rounds on other sites, mostly overseas.

At least at first glance

There is a backstory to Wujie News. The site was born in the spring of 2015 as a new propaganda tool of the Chinese Communist Party. It is under the umbrella of the Cyberspace Administration of China, also known as the Office of the Central Leading Group for Cyberspace Affairs.

The cyberspace administration was established so Xi and his leadership team could better manage and supervise online media outlets.

Wujie News was jointly set up by SEEC Media Group -- the publicity department of the Communist Party committee in the Xinjiang Uyghur Autonomous Region -- and Chinese e-commerce giant Alibaba. SEEC Media Group publishes Caijing, a leading Chinese-language business magazine.

Beijing-based Wujie News began by hiring prominent editors as well as many reporters.

Part of its job was to attract eyeballs that in the smartphone era had strayed from China's state-affiliated news outlets, known to be quite boring. The idea was to run interesting stories that would read differently -- at least at first glance -- than those put out by conventional state-affiliated media outlets, all while still toeing the official party line.

Chinese President Xi Jinping, center, and six other Politburo Standing Committee members attend the third plenary session of the National People's Congress, China's parliament, at the Great Hall of the People in Beijing on March 13.

The investigation begins

Wujie News is one of many new-breed news sites in China and one of the most successful. One reason for its stickiness might be the backing of Alibaba, which also invested in the production of one of the "Mission: Impossible" movies starring Tom Cruise.

At first, the site attracted readers with eye-catching headlines and sharp analyses -- as well as by using or quoting a bare minimum of stories from state-run media outlets such as Xinhua News Agency and the People's Daily.

"I initially thought it was a new overseas pro-China news site," a university student in Beijing said.

Only a year since going live, however, the future of Wujie News is now up in the air. There are rumors that the site could be permanently shut.

Nowadays almost all of Wujie News' stories are sourced from three major state-run media outlets: Xinhua, the People's Daily and China Central Television, or CCTV. As a result, most readers have left the site behind.

Hoodwinking the public with propaganda just is not as easy as it used to be. On Feb. 19, Xi made a rare and high-profile inspection tour of the People's Daily, Xinhua and CCTV, demanding they pledge absolute loyalty to the Communist Party.

Now Chinese authorities are investigating how that letter got posted. According to reports, more than 10 people -- including Jia Jia, a prominent Chinese commentator living in Hong Kong -- have been detained.

Jia and a male editor at Wujie News are longtime acquaintances. According to people familiar with the matter, Jia, in the U.S. at the time, noticed the letter and tipped off the editor to take it down.

When Jia returned to China in mid-March he was detained at the Beijing airport where he landed before he could transfer to a connecting flight to Hong Kong. He has since been released.

Tug of war

Lurking behind the case is the fact that many national and local leaders are increasingly anxious amid Xi's fierce and arbitrary anti-corruption campaign -- so anxious that they are afraid to do their jobs.

Premier Li referred to the situation in a government work report he delivered on March 5 during the opening session of the National People's Congress' annual meeting.

The Wujie News letter put the matter squarely on the table, giving voice to many Communist Party officials' pent-up frustrations.

In China, any public criticism of a top leader is risky. Critical words would never be posted or published while a top leader enjoys popularity. The fact that the letter made its way online reflects the erosion of Xi's once-soaring popularity.

The public now yawns at Xi's anti-corruption campaign. And the slowing economy is not doing the president any favors. If ordinary Chinese begin to feel that life is a heavier burden, many will likely turn their back on Xi.

In a democratic country, there is usually no problem with expressing opinions to a top leader. Sound criticism can even lead to better policymaking.

In China, where the Communist Party manages everything, this is not the case.

Behind the Wujie News letter is a bruising power struggle that will affect the investigation into how the missive got posted and even how the case is handled.

It also comes as Xi's enemies prepare for the Chinese Communist Party's next national congress, to be held in the autumn of 2017. Five of the seven members of the Politburo Standing Committee, the ruling party's top decision-making body, led by Xi, are due to be replaced during the event.

There is a tug of war being waged for those five seats. One of the winners could end up succeeding Xi.

So pay attention to how the investigation into the letter plays out; it could reveal who is winning the tug of war.