Protesters opposing Algerian President Abdelaziz Bouteflika’s plans to run for a fifth term in office have taken to the streets again ahead of the deadline for candidates to register.
University students in the capital Algiers were being kept behind locked gates by police.
Police are also guarding the offices of the Constitutional Council where candidates submit their files.
Mr Bouteflika, 82, said last month that he would run, sparking rare protests.
He has rarely been seen in public since suffering a stroke in 2013 and is currently undergoing medical checks in Switzerland. He does not have to be physically present to register his candidacy.
Two opposition parties, the Labour Party, and the Islamist Movement of Society for Peace, have said they will boycott the 18 April election.
On Friday about 100,000 people took part in protests against Mr Bouteflika.
Some threw stones near the presidential palace and were driven back by police firing tear gas. Some 50 police officers – and far fewer protesters – were injured.
Demonstrations also took place following Friday prayers in several other cities in Algeria.
Mr Bouteflika came to power in 1999 and is credited with putting an end to a civil war that is estimated to have killed more than 100,000 people.
Protests against food prices and unemployment broke out in 2011 during the Arab Spring but he responded by lifting a nearly two-decades old state of emergency, meeting a key demand of protesters.
After his stroke he won re-election in a poll denounced by the opposition and dissolved the country’s powerful spy agency, replacing it with a body loyal to him.
Critics say his ill health means that he is unable to perform his duties as president.
Despite the show of dissent, Mr Bouteflika is still widely tipped to win the election.