Tens of thousands of Algerians packed dozens of streets to capacity in central Algiers on Friday to challenge President Abdelaziz Bouteflika's 20-year-old rule in the biggest protests in the capital in 28 years.

While the protests were mostly peaceful, police used tear gas to block the road to the presidential palace and also used it in several other areas of the capital.

Unusually, one of the most popular imams, or prayer leaders, in Algiers did not pray for the president as he does every Friday, and only wished the best for Algeria and its people.

Algerians fed up with unemployment, corruption and an elderly elite seen as out of touch with the young have taken to the streets for the past two weeks to protest against the 82-year-old's plans to remain in office.

"Tear gas is becoming more frequent," said a witness, as teenagers on rooftops monitored police movements on the streets.