BEIJING — Chinese authorities have detained a well-known rights lawyer in a move activists described as the widening of a crackdown on individuals calling for greater accountability to fight graft — even as new accusations of official corruption surfaced.

Xu Zhiyong is the latest anti-graft campaigner to be taken away after more than a dozen detentions over the past few months have called into question the sincerity of China's new leaders' vows to scrub the Communist Party clean of graft.

What's clear, however, is that the party's anti-corruption promises could be encouraging more people to take bold steps to test the leadership's resolve. In the latest instance, a reporter for China's main state-run news agency on Wednesday launched a rare public accusation of corruption against a chairman of a state-owned conglomerate.

Chinese President Xi Jinping pledged to strike hard against corruption, and a number of high- and low-level officials have since been investigated. But there are still no signs the party is willing to undertake real institutional reforms that can fight corruption, such as requiring officials and their families to declare how much money they have and what they own.

"Xu Zhiyong's detention is likely part of the government's ongoing crackdown on groups of activists across the country who publicly call for tougher and more systematic measures to fight corruption," said Human Rights Watch researcher Maya Wang. "For calling for essentially the same things as President Xi Jinping, who vowed to bust graft, these activists are punished and detained."

She described Xu as being "very involved in the movement and widely considered as the intellectual force behind it."

Xu's view on asset declaration is hardly controversial and has also been advocated by government academics and other anti-corruption experts. But authorities appear to be wary that Xu is also advocating a movement urging Chinese citizens to build a stronger civil society, which he terms a "New Citizens Movement," and could be trying to stem its influence.

Wang Gongquan, a venture capitalist who is a close friend of Xu's, said Wednesday that he saw a detention notice that police delivered to Xu's wife on Tuesday night.

The notice said Xu was detained Tuesday evening on suspicion of gathering people to disturb order in a public place, he said. No details or causes were given to support the charge, which is often used to punish people who speak out against abuses.

Beijing police did not immediately answer faxed questions about Xu, while officers at Beijing's No. 3 Detention Center, where Xu was being held, said they weren't permitted to speak to the media.

For his activism, Xu has frequently been taken away for questioning or held under house arrest. Most recently, he had been held under house arrest since April 12 after he signed a letter in support of other activists detained for campaigning for officials to declare their assets.

Three of those activists, based in the city of Xinyu in eastern China, have been accused of illegal assembly for taking photographs of themselves holding signs urging officials to disclose their finances and calling on Xi to end dictatorship.

They could face trial at a later stage, said Zheng Jianwei, one of their lawyers. "The charge is absolutely without basis. China's constitution guarantees the right to free speech," he said.

Meanwhile, more people are taking bold steps toward exposing graft. On Wednesday, a reporter for the official Xinhua News Agency, Wang Wenzhi, publicly accused Song Lin, the chairman of China Resources (Holdings) Company, a state-owned conglomerate, and other top executives of a power generating subsidiary of deliberately overpaying for an acquisition in 2010.

The conglomerate posted a statement on its website late Wednesday in response to Wang's allegation, though without referring to any of his claims explicitly. It said reports and comments online about a deal involving one of its subsidiaries and its leaders have included "a lot of conjecture, speculation and malicious slander" that has affected the company and its top executives' reputations.

It said that the conglomerate has always operated according to national laws and regulations and acted in the interests of its shareholders and the public.

China Resources, which reported a profit of 41 billion Hong Kong dollars ($5.3 billion) last year, operates in sectors ranging from power supply and gas to real estate and medicine.

The deal "led to the loss of several billions of yuan in state-owned assets," Wang wrote on a post on his verified microblog on the popular site Sina Weibo. "Song Lin and other relevant top executives who took part in the acquisition have failed to do their duties and are suspected of corruption involving large sums of money."

The post was also carried on Xinhua's website, but both the report and microblog post were later removed. Wang could not be reached through his microblog.

Song's position is equivalent to that of a vice minister in the Chinese government, making him among the most senior officials to have come under scrutiny by efforts that appear to be independent of the party's own anti-graft agency. In May, authorities announced that an investigation had been launched into Liu Tienan, a powerful economic planning official who had been accused of corruption by a prominent journalist.