Soldiers were deployed on the streets of Libya's second city of Benghazi on Friday after thousands of people took to the streets overnight to protest about security forces killing more than 20 protesters.
In Yemen, a third protester was killed by security forces while an angry crowd reportedly set fire to a municipal building. In Bahrain, thousands of mourners called for the downfall of the country's ruling monarchy during funerals of pro-reform protesters killed by security forces.
New York-based rights group Human Rights Watch said that according to its sources inside the country, Libyan security forces had killed at least 24 people in crackdowns on protests on Wednesday and Thursday.
The killings happened after opponents of Muammar Gadhafi, Libya's leader for more than 40 years, designated Thursday as a day of protest to try to emulate uprisings in neighboring Egypt and Tunisia which ousted entrenched leaders.
A resident who lives on Benghazi's main thoroughfare, Nasser Street, told Reuters on Friday morning the city was now quiet, with no more demonstrations.
But he said: "Last night was very hard, there were a lot of people in the street, thousands of people. I saw soldiers in the street."
"I heard shooting. I saw one person fall down [from a gunshot wound] but I don't have a figure for casualties."
BBC radio, quoting an eyewitness, said doctors had counted the bodies of 10 people after the clashes in Benghazi, which is about 1,000 km east of the Libyan capital.
Another resident in Benghazi, who said he had been in contact with people in the nearby town of al Bayda, told Reuters: "The confrontation between protesters and Gadhafi supporters is still going on, some of the police have become angry. There are a lot of people killed."
Local sources had earlier told Reuters that at least five people were killed in al Bayda.
The resident also said that Saadi Gadhafi, a businessman son of the Libyan leader, had been on local radio and said he was coming to Benghazi to take over as mayor of the city and protect the people there.
Saadi Gadhafi holds senior military rank and was briefly employed as a player by Italian professional football clubs.
Funerals of those killed were expected in both Benghazi and Al Bayda on Friday. Such funerals could act as a catalyst for further protests.
Also on Friday, Witnesses in Yemen's southern port city of Aden say angry protesters set fire to the municipal building and a third demonstrator has been killed as protests stretch into an eighth day.
Hundreds of protesters demonstrated in the country's second largest city until early hours Friday demanding the ouster of the president, a key U.S. ally in battling al-Qaida.
A call spread by Facebook and Twitter is urging Yemenis to join a series of One Million People rallies on a so-called Friday of Rage in all Yemeni cities.
Protesters are demanding the ouster of President Ali Abdullah Saleh, in power for 32 years.
In Taiz, Yemen's second largest city, thousands of government supporters took to the streets Friday ahead of expected afternoon protests.
The deadly clashes in Libya broke out Thursday in several towns after the opposition called for protests in a rare show of defiance inspired by uprisings in other Arab states and the toppling of Egypt's Hosni Mubarak and Tunisia's Zine al-Abidine Ben Ali.
Tight controls on media and communications in Libya made it difficult to assess the extent of the violence, but on Friday unverified reports on social network sites said up to 50 people had died. There was no official comment on the violence.
Human Rights Watch said the Libyan authorities should respect citizens' rights to protest peacefully. "Libyans should not have to risk their lives to make a stand for their rights as human beings," the group said in a statement.
An official source in Benghazi, who did not want to be identified, said the overnight clashes took place around the city's Giuliana bridge.
"Everything is now under control. Security forces are now in the whole city and Benghazi is controlled by Saadi [Gadhafi]," the source said.
Political analysts say Libya oil wealth should give the government the capacity to smooth over social problems and reduce the risk of an Egypt-style revolt.
Gadhafi's opponents say they want political freedoms, respect for human rights and an end to corruption. Gadhafi says Libyans enjoy true democracy.
Pro-government supporters also were out on the streets early on Friday, according to CNN. The broadcaster said images transmitted on Libyan state television labelled "live" showed men chanting slogans in support of Gadhafi.
The pro-Gadhafi crowd was seen singing as it surrounded his limousine as it crept along a road in the capital packed with people carrying his portrait. Fireworks lit up the night sky.
Earlier Friday, thousands of mourners called for the downfall of Bahrain's ruling monarchy as burials began Friday after a deadly assault on pro-reform protesters that has brought army tanks into the streets of one of the most strategic Western allies in the Gulf.
The cries against Bahrain's king and his inner circle reflect an escalation of the demands from a political uprising that began just with calls to weaken the Sunni monarchy's hold on top government posts and address claims of discrimination against the Shiite majority in the tiny island nation.
The mood, however, appears to have turned toward defiance of the entire ruling system after the brutal attack Thursday on a protest encampment in Bahrain's capital Manama, which left at least five dead, more than 230 injured and put the nation under emergency-style footing with military forces in key areas and checkpoints on main roadways.
"The regime has broken something inside of me ... All of these people gathered today have had something broken in them," said Ahmed Makki Abu Taki, whose 23-year-old brother Mahmoud was killed in the pre-dawn sweep through the protest camp in Manama's Pearl Square. "We used to demand for the prime minister to step down, but now our demand is for the ruling family to get out."
Outside a village mosque, several thousands mourners gathered to bury three men killed in the crackdown. The first body, covered in black velvet, was passed hand to hand toward a grave as it was being dug.
Amid the Shi'ite funeral rites, many chanted for the removal of King Hamad bin Isa Al Khalifa and the entire Sunni dynasty that has ruled for more than two centuries in Bahrain, the first nation in the Gulf to feel the pressure for changes sweeping the Arab world.