Protesters in Bahrain appeared to gain the initiative on Saturday and mourners buried their dead in western Libya as the wave of protest washing across the Arab world tested more of the region's longtime rulers.

Unrest has spread from Tunisia and Egypt to Bahrain, Libya, Yemen and Djibouti, as people of one country after another lose their fear of oppressive, autocratic rulers and take to the streets demanding democratic change and economic opportunity.

Pro- and anti-government crowds in the Yemeni capital Sanaa hurled stones at each other and fired in the air, riot police corralled protesters in Algiers into a courtyard, and demonstrators clashed with security forces in Djibouti.

In Bahrain, a key U.S. ally and home to the U.S. Fifth Fleet, thousands of protesters regained control of Pearl Square in Manama, after first troops and then riot police withdrew from the symbolically important traffic circle.

Up to 80 people hit by rubber bullets or affected by teargas fired by the police before their withdrawal were taken to a Bahrain hospital, a doctor said.

The crown prince, charged by King Hamad on Friday with opening a dialogue with protesters, called for a national day of mourning and appealed for calm.

He had earlier announced that all troops had been ordered off the streets -- meeting one of the conditions for talks spelt out by an ex-lawmaker of the main Shi'ite opposition bloc Wefaq.

Ibrahim Mattar told Reuters the authorities must accept the concept of constitutional monarchy and pull troops off the streets before a dialogue could begin.

Then we can go for a temporary government of new faces that would not include the current interior or defense ministers, he said.

The government is led by the Sunni Muslim Al Khalifa dynasty, but the Shi'ite majority has long complained about what it sees as discrimination in access to state jobs, housing and healthcare, a charge the government denies.

The United States and top oil producer Saudi Arabia see Bahrain as a Sunni bulwark against neighboring Shi'ite regional power Iran.

In Libya, mourners in the eastern city of Benghazi were burying some of the dozens of protesters shot dead by security forces in the worst unrest of Muammar Gaddafi's four decades in power.

Human Rights Watch said 35 people were killed in the city late on Friday, adding to dozens who had already died in a fierce crackdown on three days of protests against Gaddafi's rule, inspired by the uprisings in Tunisia and Egypt.

A security source said clashes were still under way on Saturday in the region between Benghazi and Al Bayda, 200 km away.

The area is 80 percent under control. A lot of police stations have been set on fire or damaged, the source said.

New York-based Human Rights Watch said Friday's killings took to 84 its estimated death toll in three days of protests, mostly around Benghazi, against a ruling elite accused of hoarding Libya's oil wealth and denying political freedoms.

The Benghazi-based newspaper Quryna said 24 people were killed in the city on Friday, shot when security forces fired to stop protesters attacking the police headquarters and a military building where weapons were stored.

British Foreign Secretary William Hague urged Libya to stop using force against protesters and asked Middle East governments to respond to the legitimate aspirations of their people.

I condemn the violence in Libya, including reports of the use of heavy weapons fire and a unit of snipers against demonstrators, Hague said in a statement. This is clearly unacceptable and horrifying.

The spreading unrest -- particularly worries about its possible effects on the world No. 1 oil producer, Saudi Arabia -- helped drive Brent crude prices higher this week before other factors caused them to slip on Friday.

It was also a factor in gold prices posting their best weekly performance since December.

Analysts say a difference between Libya and Egypt is that Gaddafi has oil cash to smooth over social problems. He is also respected in much of the country, though less so in the Cyrenaica region around Benghazi.

There is no national uprising, said Noman Benotman, a former opposition Libyan Islamist based in Britain but currently in Tripoli. I don't think Libya is comparable to Egypt or Tunisia. Gaddafi would fight to the very last moment, he said by telephone from the Libyan capital.

In Yemen, one protester was killed and seven were hurt in clashes with supporters of President Ali Abdullah Saleh in Sanaa, a day after five people were killed in clashes between security forces and crowds demanding an end to Saleh's 32-year rule.

Saleh, a U.S. ally against a Yemen-based al Qaeda wing that has launched attacks at home and abroad, is struggling to end month-old protests flaring across the impoverished country.

In Algiers, police in riot gear crammed some 500 protesters into the courtyard of a residential block before they could reach May 1 Square in the city center to start a banned march.

The main opposition parties did not take part in the protest, which was organized by human rights groups, trade unionists and a small opposition party.

This, like other recent demonstrations in Algeria for democratic change and better economic conditions, was too small to rattle the authorities, but there are signs that pressure is building within the ruling group for substantial change, including a new government line-up.

The political uprising sweeping through the Middle East has also reached the tiny Horn of Africa state of Djibouti, where anti-government protesters clashed with security forces on Saturday for the second day running.

On Friday, thousands of protesters called for the removal of President Ismail Omar Guelleh, whose family has held sway in Djibouti since independence in 1977. Guelleh took office in 1999 and is expected to run for a third term in April 2011.

Djibouti, a former French colony between Eritrea and Somalia, hosts France's largest military base in Africa and a major U.S. base. Its port is used by foreign navies patrolling busy shipping lanes off the coast of Somalia to fight piracy. Unemployment runs at about 60 percent.

(Additional reporting by Hamid Ould Ahmed in Algiers, William Maclean in London and Saleh Al-Shaibany in Muscat; Writing by Tim Pearce, editing by Angus MacSwan)