Thousands of police in riot gear poured into the centre of the Algerian capital on Saturday to stop a planned demonstration from copying the uprising which forced out Egyptian President Hosni Mubarak.

A group of about 20 protesters managed to reach the square where the protest march is scheduled to start later, and shouted "Bouteflika out!" -- a reference to the Algerian president -- before police in riot gear arrested some of them.

Officials have banned the opposition march, setting the stage for possible clashes between police and demonstrators who are demanding greater democratic freedom, a change of government and more jobs.

Mubarak's resignation on Friday, and last month's overthrow of Tunisia's leader, have electrified the Arab world and led many to ask which country could be next in a region where an explosive mix of authoritarian rule and popular anger is the norm.

Widespread unrest in Algeria could have implications for the world economy because it is a major oil and gas exporter, but many analysts say an Egypt-style revolt is unlikely because the government can use its energy wealth to resolve most grievances.

"I am sorry to say the government has deployed a huge force to prevent a peaceful march. This is not good for Algeria's image," said Mustafa Bouachichi, a leader of the League for Human Rights which is helping organize the protest.

The protest is scheduled to begin at the May 1 Square, in the centre of Algiers near the port, at 11:00 a.m.

Two hours beforehand, a police helicopter hovered over the neighborhood and about 200 officers in helmets and armed with batons were at the square. Dozens of police vehicles were parked nearby.

Thousands more police were on stand-by in other parts of the city, which overlooks the Mediterranean Sea.

Near Kennedy Square, about 3 kilometers from the centre, police outnumbered local residents. They milled around in riot gear, drinking coffee, smoking and reading newspapers.

Ripple Effect

Other Arab countries have also felt the ripples from the revolts in Egypt and Tunisia. Jordan's King Abdullah replaced his prime minister after protests and in Yemen, President Ali Abdullah Saleh promised opponents he would not seek a new term.

Protest organizers in Algeria -- who say they draw some of their inspiration from events in Egypt and Tunisia -- say police may turn people away before they can reach the march in the capital, or parallel protests planned for other cities.

"Algerians must be allowed to express themselves freely and hold peaceful protests in Algiers and elsewhere," rights group Amnesty International said in a statement.

"We urge the Algerian authorities not to respond to these demands by using excessive force."

The government says it refused permission for the rally for public order reasons, not because it is trying to stifle dissent. It says it is working hard to create jobs, build new homes and improve public services.

In an attempt to head off anti-government unrest, the authorities have cut prices for sugar and cooking oil, bought huge quantities of grain to ensure bread supplies and promised to lift a 19-year-old state of emergency.

Saturday's protest is not backed by Algeria's main trade unions, its biggest opposition parties or the radical Islamist groups which were banned in the early 1990s but still retain grassroots influence.

The march "is likely to be violent, but unlikely to destabilize the regime," said Eurasia Group, a political risk consultancy.