AMMAN (Reuters) - Thousands of demonstrators chanted the Arab Spring slogan "the people want the downfall of the regime" in Jordan on Friday, although a day billed as the culmination of three days of protests passed off largely in peace.
Jordan has so far largely avoided the unrest that has swept across the Middle East over the past two years, but a decision this week to raise fuel prices led to the demonstrations.
The mainly urban Muslim Brotherhood announced on Friday it was joining the protests, lending the voice of the country's largest opposition movement to demonstrations which had previously been focused on rural and tribal areas.
Friday's protest near the main Husseini Mosque in downtown Amman was peaceful, with unarmed police separating the demonstrators denouncing King Abdullah from a smaller crowd chanting in support of the monarch.
"Go down Abdullah, go down," the main crowd of about 3,000 protesters chanted as police, some in riot gear, largely stayed away from crowd.
"Raising prices is like playing with fire," said one banner.
Abdullah cancelled a visit to London he had been due to make next week, Britain's Foreign Office said, without giving further details.
U.S. Secretary of State Hilary Clinton phoned the monarch and backed his efforts to accelerate political reforms in the kingdom and implement economic reforms, a palace statement said.
A friend of the West, the monarch is seen by many Jordanians as a bulwark of stability, balancing the interests of native tribes and the increasingly assertive Palestinian majority.
Instability in Jordan would come at a dangerous time for the region, when Syria's war risks spilling across borders and Israel is bombing Palestinians in Islamist-run Gaza.
Witnesses said other Friday protests also ended peacefully in the northern city of Irbid and in restive southern towns of Karak, Tafila and Maan, dispelling fears of wider civil unrest.
"The government succeeded in frightening people of chaos and many people were discouraged by what they see as the alternative, as chaos," said Lamis Andoni, a political analyst.
Protests had turned violent in impoverished towns across the kingdom since Wednesday when the government imposed a rise in the price of fuel. Unemployed youths and demonstrators have attacked police stations, closed roads with burnt cars and torched government buildings. One protester was killed on Thursday as a crowed tried to storm a police station in Irbid.
Most of the civil unrest has taken place in outlying areas inhabited by tribes, Jordan's original inhabitants who now form a minority outnumbered by Jordanians of Palestinian origin.
The tribes supply the army and security forces with recruits and form the backbone of support for the ruling Hashemite dynasty. They are seen as wary of the prospect of democratic reforms that would cost them privileges and state jobs.
The Brotherhood are rivals to the tribes for power, and their decision to back protests signalled discontent spreading, although senior Brotherhood figures did not appear in person.
"King Abdullah should take note of the situation by going back on the decision to raise prices. The Jordanian people are unable to shoulder more burdens," Brotherhood leader Sheikh Hamam Said said in a statement ahead of the protests.
The slogan "the people want the downfall of the regime" has emerged as the main chant of Arab Spring demonstrations that toppled autocrats from Tunisia to Yemen, in many cases bringing to power elected Islamists allied to the Brotherhood.
In Jordan, an opposition of liberals and Islamists has generally sought reforms, rather than the overthrow of the 50-year-old king, in power since 1999.
Abdullah accepted constitutional changes in August that devolved some of his powers to parliament, paving the way for a prime minister emerging from a parliamentary majority rather than one handpicked by him. However, urban politicians say he has been constrained by the tribes and slow to adopt reforms.
The Brotherhood is planning to boycott a parliamentary election set for January, arguing that rules were designed to safeguard tribal power by giving too many seats to rural areas.
Like many Arab states, Jordan has used government subsidies to appease people with cheap food and fuel, only to court unrest when the cash runs out.
Lifting the subsidies "deprives Jordanians of the minimum requirements of a decent living," Said said. "The King should speed reforms that restore power to the people to allow it put the corrupt on trial and restore embezzled money to the people."
Additional reporting by Khaled Yacoub Oweis and Tim Castle in London; Editing by Peter Graff and Myra MacDonald