Police beat up pro-democracy activists and arrested 240 members of the Muslim Brotherhood, including two of its leaders, in a crackdown against protests Thursday in support of two pro-reform judges.

As the violence broke out in the streets of the capital, a disciplinary court reprimanded one of the judges and cleared the other. The two were referred to the panel after speaking out against fraud during last year's parliamentary elections, making them heroes to reform advocates.

In another blow to the pro-democracy movement, a separate court rejected the appeal of Ayman Nour, the runner up in last year's presidential elections. That means he will have to serve a five-year sentence for a forgery conviction on what he claims were trumped up charges to eliminate him from the political scene.

The prosecution of Nour has strained ties with the United States, which denounced his conviction in February and called for it to be reviewed.

CountryWatch: Egypt

Last week, Washington also criticized Egypt, a top ally in the Mideast, for a similar police crackdown against protesters supporting the two judges. Some 255 people were arrested during those demonstrations.

Protests in support of the two judges -- Hesham el-Bastawisy but cleared Mahmoud Mekki -- have sparked a harsh police response over the past three weeks amid accusations that President Hosni Mubarak has backed off promises to bring greater democracy.

In Thursday's violence, thousands of riot police and hundreds of plainclothes officers were deployed in streets leading to the courthouse in downtown Cairo to prevent protesters from gathering for the judges' hearing.

Plainclothes police plunged into a crowd of demonstrators and beat them to the ground with batons. Protesters who had been chanting slogans against Mubarak fled, some clambering over cars to get away as police chased them.

"I didn't do anything,"one middle-aged man screamed as plainclothes police held him by the collar and beat him. Nearby an officer slapped a young man on the back of his head.

The Interior Ministry said in a statement Thursday that it had detained 240 members of the Brotherhood, saying they had sought to "create unrest and chaos." It said protesters were "chanting hostile slogans."

The Brotherhood said police arrested 500 of its members Thursday, including two top leaders: Essam el-Erian and Mohammed Morsi. Police beat Morsi as he participated in the protests, said Brotherhood lawmaker Hamdi Hassan.

El-Erian was arrested last spring during a countrywide wave of protests and incarcerated for several months. Authorities released him after Egypt's presidential elections last fall.

Police also detained a 26-year-old man named Hassan Ibrahim Hassan as he was headed to the downtown courthouse wearing a belt with "wires and children's fireworks connected to it," the Interior Ministry said.

The judicial disciplinary panel found el-Bastawisy guilty of libeling his colleagues by making fraud accusations and gave him a reprimand, the lightest possible punishment for the judge, who could have faced dismissal. The panel cleared Mekki.

Neither of the judges, who are members of Egypt's highest court, attended the sesssion. El-Bastawisy was in a hospital recovering from emergency heart surgery Wednesday.

Mekki denounced the ruling, saying "it runs contrary to all judicial traditions." He told The Associated Press that the reprimand against his colleague "has a moral and psychological effect, but it will not affect his job in any way."

"They should have honored him for what he has done," he said.

At another Cairo court, a judge rejected the appeal by Nour, who was sentenced to five years in prison on forgery charges after he came in second to President Hosni Mubarak in September elections.

The leader of Nour's al-Ghad party, Nagi el-Ghatrifi, said the ruling "reflects the Egyptian regime's persistent rejection of any serious reform and its exploitation of the international community's leniency with Egypt."

The appeal court judge said the ruling was final, and Nour's wife Gameela Ismail -- also a prominent figure in his al-Ghad party -- said there was no further legal recourse.

"There is nothing we can do except to continue to struggle for reform," she told AP.

Shortly after the verdict became known, a group of Nour supporters demonstrated in the street outside the al-Ghad party offices, shouting insults against Mubarak and the government. Police arrested 14 protesters, police said.

Thursday's protests, which broke out in several parts of the capital's downtown area, brought out members of secular reform groups and the fundamentalist Brotherhood, Egypt's strongest opposition movement

"This is not only the judges' battle, but that of everyone and the judges are at the forefront," Brotherhood parliamentarian Mustafa Mohammed said. "The regime has made it a habit to bring out the security forces to prevent people from expressing their opinion and deprive them of their freedom."

Sayed Abdel Atti, 29, an al-Ghad member, held up a banner and pronounced, "I am ready to be arrested or face anything bad they do to me."

"We want to see someone else other than him," Abdel Atti said, referring to Mubarak. "We want change."