BEIJING - Chinese authorities tried one of the country's most prominent human-rights lawyers behind closed doors on Monday morning, as police roughed up protesters, journalists and diplomats who gathered outside a Beijing courthouse hoping to observe the proceedings.

Prosecutors have charged Pu Zhiqiang, 50, with "picking quarrels and provoking trouble" and "inciting ethnic hatred" over seven microblog posts that he penned between 2011 and 2014.

Pu, known as China's "Giant Lawyer" for his commanding height and baritone voice, has gained a massive following online as a bold and acerbic critic of government policy. He could face up to eight years in prison; human-rights groups have called his case a government attack on free expression and dissent.

"[Pu] admitted the seven microblogs were written by him, there was no issue with it, this is a fact," Pu's attorney, Mo Shaoping, told the Reuters news agency. "Secondly, he said that if these microblog posts had caused injury to other people, he apologizes for it. Thirdly, he had no intention to incite ethnic hatred or pick quarrels and provoke trouble."

The court has not announced a verdict or sentence in the case.

On Monday, dozens of police, uniformed and plainclothes, guarded the streets surrounding the court, wearing down coats and antipollution face masks. Soon after the trial began, police began violently shoving a crowd of journalists and diplomats - including representatives from the United States, European Union, and Australia - away from the courthouse gates.

The U.S. Embassy is "concerned" about the "vague charges" leveled against Pu, Dan Biers, deputy political counselor at the embassy, told a small scrum of reporters as police shoved and shouted "go" to drown out his words. "Lawyers and civil society leaders such as Mr. Pu should not be subject to continuing repression but should be allowed to contribute to the building of prosperous and stable China," he said.

"We urge Chinese authorities to release Mr. Pu," Biers said, repeating his statement about 100 feet down the road, "and call upon China to uphold fundamental human civil rights and fair-trial guarantees as enshrined in the [Chinese] constitution and its international human rights commitments."

The Foreign Correspondents' Club of China said in a statement that the authorities' "effort to deter news coverage is a gross violation of Chinese government rules governing foreign correspondents."

"Legal coverage is a normal part of journalistic work and is expected grow as China pushes to develop its rule of law," it said.

About a block away from the courthouse, a few dozen protesters raised signs denouncing Chinese police and calling for democracy and improved human rights. "Pu Zhiqiang is not guilty!" they chanted. At least two protesters were detained.

Authorities detained Pu in May after he participated in a private commemoration of the 25th anniversary of the Tiananmen Square massacre, when soldiers opened fire on peaceful pro-democracy protesters. He was formally arrested in June.