MANAMA, Bahrain - Thousands of anti-government protesters marched to Manama's Pearl Square on Wednesday after Bahrain's king released at least 100 political prisoners, an acknowledgment by the Sunni ruler of the mounting pressure being placed on him by the Shiite opposition.
The inmates included 25 Shiite activists on trial since last year for plotting against the state. The release underlined how much the absolute rulers of the Gulf kingdom, a close ally of Washington, want to get reform talks with protest leaders under way. Their release was one of the major demands of the emboldened political movement seeking constitutional reform.
Bahrain's authorities said in an e-mail that 308 prisoners were released from custody on Wednesday. However, the president of Bahrain's Center for Human Rights, Nabeel Rajab, said only about 100 of those people were political prisoners, while at least 300 remain in detention.
Rajab speculated that the other inmates who were let go may have been criminals who were being held on nonpolitical charges.
Amid concerns that the island nation's uprising could spread to Saudi Arabia, where the monarchy permits few political freedoms, Bahrain state media reported that King Hamad bin Isa Al Khalifa was holding talks on the unrest with the Saudi king in Riyadh.
Like tiny Bahrain, OPEC heavyweight Saudi Arabia also has a significant Shiite population that has long complained of oppression by Sunni rulers. Shiites far outnumber Sunnis in Bahrain, which has just 525,000 residents.
U.S. Secretary of State Hillary Rodham Clinton said the United States welcomed the king's decision to release the prisoners and to "initiate a meaningful dialogue with the full spectrum of Bahraini society."
Hamad ordered the release on Tuesday. He also halted trials against the activists.
Two of those in the case were being tried in absentia, including prominent opposition leader Hassan Meshaima, who has been in self-exile in London since last year.
Meshaima's return to Bahrain was imminent, his supporters said, but his son Ali Meshaima told The Associated Press on Wednesday his father was in Lebanon due to questions about whether he is still wanted by the Bahraini authorities.
The activist's presence could bolster opposition forces seeking a harder line against the Bahrain dynasty, including some who have called for the complete ouster of the king and the Al Khalifa family.
Meshaima's group, known as Haq, is considered more radical than the main Shiite political bloc that has taken a central role in the revolt and is seeking the establishment of a constitutional monarchy.
Sheik Mohammed Habib al-Mugdad, a prominent Shiite cleric who was among those released from custody on Wednesday, headed the prisoners' march to Manama's landmark square that has become the center of the protest.
Although the event was smaller than a huge protest that flooded downtown Manama on Tuesday with protesters waving Bahrain's red-and-white flag, the march was politically significant in a country where the imprisonments were not publicly discussed.
Inspired by the Egyptian uprising that toppled Hosni Mubarak, protesters have set up an encampment in Pearl Square like the one in Cairo's Tahrir Square.
Al-Mugdad, who was detained in August, told reporters he was tortured and repeatedly beaten in custody. He showed signs of what he said were electric shocks on his chest, stomach and legs.
He said he spent three months in solitary confinement because he had criticized the government for "denying rights to Bahrainis and not sharing wealth."
"I faced torture because they wanted to silence me," al-Mugdad said. "They did not succeed and I am marching with my people, joining them in a peaceful protest to get our rights."
The government said in its e-mail that it takes allegations of mistreatment in custody "extremely seriously" and is "committed to thoroughly investigating all and any claims made."
Bahrain's Shiite community has complained of discrimination and political persecution in the kingdom. It has staged protests in the past, but the latest unrest is the most serious challenge to the Sunni monarchy.
The Health Ministry estimates seven people have been killed since security forces opened fire on the protesters who first took their grievances to the streets on Feb. 14.
The attacks on protesters have been heavily criticized by Bahrain's Western allies, including the United States. The U.S. maintains very close ties with Bahrain, which hosts the U.S. Navy's 5th Fleet.