Algerian authorities have been deploying large numbers of police and arresting protesters to prevent demonstrations in the capital ahead of the upcoming presidential elections, Human Rights Watch said.
The New York-based rights group said on Monday that officials have recently targeted a movement opposed to a fourth term for President Abdelaziz Bouteflika.
The 77-year-old president will be running after 15 years in power, despite having a stroke last year that has made his speech and movement difficult.
While six candidates have been approved for the April 17 elections, Bouteflika is expected to win with the backing of the powerful machinery of the state.
Human Rights group said that security personnel in Algiers have used force three times this month to disperse supporters of the Barakat [Enough] movement, as they expressed their opposition to a new mandate for Bouteflika.
"On March 1, 4, and 6, security forces tried to block access to the protest site. Security forces confronted protesters who managed to reach the site and started to wave banners and chant slogans," the organisation said in a statement.
Human Rights Watch urged authorities to rescind the 2001 decree banning all demonstrations in Algier. It also called on it to create conditions for unfettered debate and competitive elections.
"The open-ended, blanket ban on demonstrations in the capital has been in effect almost as long as Bouteflika has been president," said Eric Goldstein, deputy Middle East and North Africa director at Human Rights Watch.
"Is it any surprise that these latest victims of the crackdown on protest are those who peacefully oppose his election to a fourth five-year term?"
On Saturday, supporters and opponents of Bouteflika's decision to seek a fourth term staged rival demonstrations in Algiers.
Around 3,000 supporters of the president gathered in the capital for what they called "a national meeting to sensitise young people to voting".
They screened a documentary about Bouteflika's 15 years in power, and his former prime minister and election campaign manager Abdelmalek Sellal gave a speech.
On the other side of the city, hundreds of opponents of Bouteflika's re-election bid also held peaceful marches.
Three different opposition marches took place, with the largest organised by the Barakat movement, which was formed specifically to oppose Bouteflika seeking another term.
The protesters marched under the slogan "Enough of this election masquerade".
Despite Barakat's small numbers and the heavy opposition it faces from a powerful state, local analysts are describing it as an important development.
They say it brings to mind Egypt's Kifaya (which also means "enough") movement against President Hosni Mubarak that eventually led to the uprising that overthrew the government.
"It is an alternative to the classic political parties that have failed and it makes us think of the youth behind the Arab Spring in Tunisia and Egypt,'' said Rachid Tlemcani, a political analyst at University of Algiers, who said the movement's rough treatment by authorities showed the system's insecurity.
"It is afraid that this movement could be a catalyst for a wider conflagration because all the ingredients for an explosion are there."
Algeria was barely affected by a wave of pro-democracy protests that swept the Arab world in 2011, in part many say because of a decade-long battle against an Islamist uprising in the 1990s that left 200,000 dead.