A group of Algerian opposition supporters trying to hold a protest clashed with police in the capital and several people were injured, protest organisers and official media said on Saturday.
The protest was scheduled to take place just over a week after a wave of demonstrations in neighbouring Tunisia forced that country's long-standing president to flee, sending shockwaves through the Arab world.
The head of the RCD party, the biggest opposition group in Algeria's parliament, said party officials were surrounded by riot police when they tried to leave their headquarters building to go to the planned protest.
"We have 32 injured, including a member of parliament," party chief Said Saadi told Reuters by telephone. "We have been prevented from marching by an impressive security apparatus. More than 1,500 (police) were on the streets of Algiers."
After the clash with police, a small group of RCD supporters remained outside the party headquarters chanting "The authorities are assassins!" and "A free and democratic Algeria!"
Algeria's official APS news agency quoted a police source as saying arrests had been made and that seven police officers had been injured, two of them seriously.
Authorities in Algeria, a major exporter of energy, had earlier refused permission for the protest, saying it would disturb public order. They had urged members of the public to "ignore ...provocative acts."
At the planned venue for the protest, on May 1 Square near the centre of Algiers, only about 15 protesters showed up, a Reuters reporter at the scene said.
Nevertheless, several hundred police in full riot gear were on standby in vehicles nearby, and a police helicopter hovered over the centre of the city.
Algeria's opposition says the state is failing to invest energy revenues in improving peoples' standard of living, that it imposes restrictions on political parties and that the army is too powerful.