Algerian police on Friday threw up a tight cordon around a key protest site, arresting dozens of demonstrators in the biggest show of force in 14 weeks of mass demonstrations.
Protestors have rallied outside the Grand Post Office in Algiers every week since February, forcing veteran president Abdelaziz Bouteflika to step down in early April after two decades in power.
They have continued to stage mass demonstrations each Friday, demanding sweeping reforms and the departure of regime figures including army chief Ahmed Gaid Salah and interim President Abdelkader Bensalah.
But ahead of this week's protest, security forces erected fences in a bid to prevent demonstrators from accessing the site.
Several hundred protesters gathered near the building, chanting: "Tired of the generals!" "Gaid Salah resign!"
However, they were kept at bay by a police cordon and a row of vehicles, and an AFP journalist saw a woman arrested nearby.
"Patrols criss-crossed the city and arrested anyone suspected of joining" protests, said Said Salhi, vice-president of the Algerian League for the Defence of Human Rights, on Twitter.
"It seems they want to ban the rally."
But despite the arrests and the hardships of demonstrating during the Islamic fasting month of Ramadan, huge crowds filled the streets of Algiers.
Mehenna Abdeslam, a protester and a university teacher, told AFP he saw "the police systematically arrest anyone carrying a banner".
But he said that would not stop Algerians demonstrating.
Local news site TSA reported police in Algiers had made "massive arrests among the protesters".
It also noted a heavy presence of female police officers for the first time since the protests began.
An activist with Algeria's Socialist Workers' Party wrote on Facebook that he was being held "with some 20 other citizens in a police van".
The official APS news agency reported protests in 25 out of the North African country's 48 regions, with further rallies expected in the desert south during the cooler evening hours.
Most protesters in Algiers dispersed peacefully later in the day.
A presidential election originally due to take place in April is set for July 4, but protesters reject it, saying a vote will not be valid until new, independent institutions are set up to oversee voting.
As the deadline for candidates to register approaches, no major prospect has stepped forward.
While Bensalah and Prime Minister Noureddine Bedoui have remained relatively quiet, Salah has given three speeches in as many days this week.
On Monday, he spoke out against the protesters' demands, saying calls for the departure of key members of the Bouteflika-era ruling circle were "unreasonable, even dangerous".
Preparations for the presidential poll should be accelerated to avoid "the trap of a constitutional void", he said, adding that the ballot would "stop those who are trying to prolong this crisis".
On Tuesday, he called on protesters to "unite" with the army to prevent "instigators" from hijacking the demonstrations, and on Wednesday he reassured the public he had "no political ambition".
Some observers have pointed to similarities with Egypt's general-turned-president Abdel Fattah al-Sisi, who was elected in 2014 despite vowing the army would stay out of politics after it ousted Islamist president Mohamed Morsi the previous year.
In Algeria, the army has played a central role since the country's independence in 1962, and was considered the real holder of power up until Bouteflika was first elected in 1999.