Bahraini troops opened fire on protesters Friday, with unknown numbers killed or wounded, witnesses said, and protests also spread in Libya, Yemen and Algeria.
Iran's Press TV reported that at least 30 people were killed or wounded by live ammunition in Bahrain. Britain's Daily Telegraph said at least four people died. Other reports had five or more killed.
Al-Jazeera reported that ambulances could not reach the wounded.
The Telegraph report described the protesters as "utterly routed and bloodied."
Thousands of Bahrainis marched in a funeral procession for four pro-democracy protesters Thursday.
Human Rights Watch said at least 24 people were killed in "Day of Rage" protests Thursday in Libya. There were protests in several locations, including Tripoli, Benghazi, al-Bayda, Zenten, Dema and Ajdabiya.
The Committee to Protect Journalists, based in New York, said authorities in Bahrain and Yemen escalated attacks on the news media to censor coverage of the spreading protests, a report in Britain's Guardian said.
In Yemen, at least four protesters were killed by security forces in Sanaa on Thursday.
Amnesty International said at least six demonstrators were reported seriously wounded in Ta'izz Friday when security forces attacked them with a hand grenade.
On Friday, thousands of Shiites gathered at a mosque in Sitra, Bahrain, and in Manama, the capital city, to attend funerals of people killed the previous day, The New York Times said.
Bahrain's army deployed tanks and armored personnel carriers around the capital's main intersection, Pearl roundabout, the equivalent to Cairo's Tahrir Square, in an effort to deter protesters from gathering there, the Financial Times reported.
Government troops patrolled the capital Friday morning, witnesses said.
In the United States, the administration of President Barack Obama pressed Bahrain to show restraint. U.S. Secretary of State Hillary Clinton called Bahraini Foreign Minister Khaled bin Ahmed al-Khalifa to convey Washington's "deep concerns" about the repression of peaceful demonstrators. Clinton said she stressed how important it would be for Friday funerals and prayers not to "be marred by violence."
Human Rights Watch called on Bahrain's King Hamad al-Khalifa to halt the attacks on demonstrators since the protests began Monday.
"There is absolutely no excuse for this escalating use of deadly force and apparent misuse of weapons like tear gas against sleeping people," said Sarah Leah Whitson, director of the organization.
Whitson was referring to a pre-dawn raid by security forces to disperse protesters in what was described by authorities as an "illegal encampment."
The rights group also appealed to Libya to halt the use of lethal force.
"The security forces' vicious attacks on peaceful demonstrators lay bare the reality of [Libyan leader] Moammar Gadhafi's brutality when faced with internal dissent," Whitson said.
Mohammad Ali Abdellah, the deputy leader of an exiled opposition group, the National Front for the Salvation of Libya, told The New York Times in a telephone interview from London that roads leading to Green Square in central Tripoli had been closed and people living in the vicinity were warned in text messages from the authorities not to join any protests.
Libya's military was reported mobilized, with commando teams sent to likely trouble spots and armored personnel carriers taking up positions on key roads near cities. The official state Jamahiriya News Agency, known as JANA, said pro-government rallies were being organized to express "eternal unity" with Gadhafi.
In Algeria, opposition leaders declared they would hold a protest march in Algiers, Saturday, even though the government promised to lift a state of emergency.
Unrest continued to spread in Iraq, with new protests erupting in several cities after reports indicated private security guards in the Iraqi Kurdistan city of Sulaimaniya fired on a group of protesters who tried to storm the political offices of the region's leader.
Protesters say they want better government services, including more electricity, and in some cases they demanded that local government officials resign.