People face police officers as they protest against the country's leadership, in Algiers. The protest movement has been overwhelmingly peaceful but police were out in larger than usual numbers Friday and the atmosphere was strained. Picture: Thibault Camus/AP

Algiers - Hundreds of thousands of protesters rallied in Algiers for an eighth successive Friday to demand the departure of the ruling elite, witnesses said, as Algeria prepares for a presidential election in July.

Police in anti-riot gear fired tear gas in the evening to disperse a crowd of several hundreds of youths in the city centre, witnesses said, after an otherwise largely peaceful march joined by families throughout the day.

Police arrested 108 people after clashes with "infiltrators" among the protesters who injured 27 policemen, a police statement said.

President Abdelaziz Bouteflika stepped down after 20 years in power 10 days ago, bowing to pressure from the army and weeks of demonstrations mainly by young people seeking change in the North African country.

But the protests, which began on Feb. 22 and have been largely peaceful, have continued as many want the removal of an elite that has governed Algeria since independence from France in 1962 and the prosecution of people they see as corrupt figures.

Anti-riot police confront some youths after a protest in Algiers. Picture: Ramzi Boudina/Reuters

Bouteflika has been replaced by Abdelkader Bensalah, head of the upper house of parliament, as interim president for 90 days until a presidential election on July 4.

"No to Bensalah," the protesters chanted on Friday.

Reuters correspondents at the scene estimated the crowd size at hundreds of thousands of people as on previous Fridays, although there was no official count.

"We want the prosecution of all corrupt people" and "no to the gang", said banners held up by marchers. Many protesters waved Algeria's white, green and red crescent moon flag.

Anti-riot police fire tear gas as they confront some youths after a protest in Algiers. Picture: Ramzi Boudina/Reuters

One of them, who gave his name as Nawal, told Reuters: "We came out today to say that Bensalah's position is unconstitutional."

"We do not deserve military rule. We deserve a democratic and free Algeria."

Ali Badji, a 52-year-old grocer, holding his son on his shoulders, said: "We are still sticking to our demands. We want a radical change."

State television said similar marches took places in most cities.

Police said on Friday in a statement it had arrested an unspecified "terrorist group" and also some foreigners who had planned to incite protesters to violence. It gave no details.

Tens of thousands of Algerians chant slogans during a demonstration against the country's leadership in Algiers. Picture: Toufik Doudou/AP

More than one in four people under the age of 30 are unemployed - one of the central grievances of protesters who want the economy liberalized and diversified to reduce its reliance on its oil and gas production.

On Wednesday, Algeria's army chief, Lieutenant-General Ahmed Gaed Salah, said he expected to see members of the ruling elite close to Bouteflika, who he called a "gang", prosecuted for corruption and said he would support a transition toward elections.

The army initially monitored the unrest from the sidelines. Then Salah intervened, declaring Bouteflika - rarely seen in public since suffering a stroke in 2013 - unfit to rule.