In Sohar, security forces drove away protesters who had been keeping vigil at the Earth Roundabout, a landmark intersection where at least one protester was killed in clashes on Sunday.
It came a day after the United States urged Oman to show restraint and press ahead with reforms in the strategic ally on the busy Strait of Hormuz oil shipping lane.
Security forces initially cleared protesters from the main coastal highway linking Muscat to Sohar, 200 kilometres (125 miles) northwest of the capital.
But protesters continued to deploy trucks blocking access from Sohar port, Oman's second largest, to nearby aluminium and petrochemical factories.
Armoured vehicles deployed at the Earth Roundabout, where protesters had kept vigil for a third consecutive night.
The protesters held placards demanding jobs and salary increases and also called for ministers they accuse of corruption to be tried. Some also waved Omani flags and carried portraits of Sultan Qaboos.
Protests were also reported in the southern port of Salalah and the northwestern oasis region of Buraimi.
In Salalah, some 200 people demonstrated outside the office of the governor of Dhofar province, demanding an increase in wages and benefits, and dozens of protesters staged a similar rally in Buraimi.
Some 300 protesters also staged a sit-in outside the sultanate's consultative council in Muscat, demanding an end to corruption.
The demonstration, organised by intellectuals and non-governmental associations, came shortly after thousands marched in the capital vowing support for Sultan Qaboos.
"No to wasting public money" and "Government corruption should be fought," said banners carried by protesters.
Normally placid Oman is the latest country to be hit by the wave of popular protests that has rattled several Arab countries and swept from power the leaders of Tunisia and Egypt.
Mass demonstrations also threaten the regimes of Bahrain, Libya and Yemen.
State news agency ONA said rioting had begun at dawn on Saturday and continued on Sunday. Protesters said as many as five people died on Sunday, but officials insist only one person was killed.
The protesters insist they are not challenging the rule of Sultan Qaboos, who has been in power since 1970, but are merely calling for jobs and reform.
The violence has prompted the United States and human rights watchdog Amnesty International to call for restraint.
"We have been in touch with the government and encouraged restraint and to resolve differences through dialogue," State Department spokesman Philip Crowley said on Monday in Washington's first reaction to the unrest.
Also on Monday, Amnesty urged Oman, which it said has "used excessive force," to rein in its security forces and order "an immediate independent investigation."
"The government must respect the right of people to engage in peaceful protest and ensure that they can do so without fear or threat," said Malcolm Smart, director of the group's regional programme.
In a move aimed at addressing the grievances of protesters, Qaboos has announced the creation of 50,000 new jobs and a monthly allowance of 150 riyals (390 dollars/283 euros) for registered job seekers.
He also ordered the formation of a ministerial committee to draw up proposals to meet calls for the elected consultative council to be given more powers.
Late on Tuesday, the government said the new jobs will be assigned to those registered before February 27 and will be in the public and private sectors, while the monthly allowance will be paid as of the beginning of this month.
"The private sector should cooperate with the efforts exerted by the government to give jobs to citizens searching work," it said in a statement carried by ONA state news agency.
Oman guards the strategic Strait of Hormuz through which 40 percent of the world's oil supply passes and Muscat is a key Western ally in the region. Iran borders the waterway's northern flank.
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