Thousands of Algerians gathered on Friday chanting slogans against ailing President Abdelaziz Bouteflika's bid for a fifth term, despite the defiant leader's warning of the risk of "chaos".
Waving Algeria's green, white and red flag, men and women converged on the city's landmark Grand Post Office square, as youths staged a peaceful march, AFP journalists said.
Security in Algiers was tight, with anti-riot vehicles out in force, alongside a water cannon, as a police helicopter hovered overhead, although the past two weeks of demonstrations have been mostly calm.
In a message released on the eve of the fresh protests, Bouteflika warned that trouble-makers may try to infiltrate the demonstrations.
"Many of our fellow citizens" have demonstrated across the North African country "to peacefully express their views", he said.
"However, we must call for vigilance and caution in case this peaceful expression is infiltrated by some insidious party... which could cause chaos," he said, without mention of the demands that he abandon his bid to seek re-election.
Bouteflika flagged the risk of a return to the "national tragedy" of Algeria's decade-long civil war in the 1990s and of the "crises and tragedies caused by terrorism" in neighbouring countries.
Algeria has largely avoided the conflicts unleashed by the Arab Spring uprisings that brought down rulers in neighbouring Tunisia and Libya.
But discontent, particularly among the country's youth, turned to anger after the veteran leader announced on February 10 that he would seek another bid for power.
Calls have circulated widely on social media under the hashtag "#March 8 Movement" for massive but peaceful demonstrations in the capital and cities across the North African state.
"I will not throw a single stone!" and "No windows will be smashed," were among "18 commandments" sent out to participants by poet and writer Lazhari Labter, as well as instructions to clean up streets after the protests.
He also called for demonstrators to turn the event into "a day of celebration" and one of "love, faith, Algerian flags and roses".
Volunteers have signed up to marshal protest routes, provide first aid and to clean up, while drivers have offered to shuttle participants to venues from outside city centres.
The country's leaders "will not give in easily, but we won't either", said a taxi driver, summing up the popular mood.
He said that on February 22, at the first Friday protests, less than half the residents of his district of Algiers had turned out.
"On March 1, about two out of three said they would march, and (now) 100 percent of people are saying they will be out on the streets," he said, declining to be named.
Bouteflika uses a wheelchair and has rarely been seen in public since suffering a stroke in 2013, and his bid to secure another term at the April 18 election has sparked waves of protests.
Despite a ban dating back to 2001, demonstrations have been staged almost daily in Algiers since a massive rally two weeks ago.
Bouteflika has been in Switzerland since February 24 for what the presidency has described as "routine medical tests", and a date for his return home has not yet been announced.
His latest message came Thursday as around 1,000 lawyers took to the streets of Algiers, arguing that his ill health should disqualify him from the race.
They breached police cordons to march on the Constitutional Council, the body responsible for approving the candidacy of those registered to contest the poll.