Many demonstrator young and unemployed, expressing frustration with the ruling party and income inequality.
Thousands of Angolans have protested against what they say was a flawed election last month that returned the ruling MPLA to power, continuing its nearly five decades of uninterrupted rule
Saturday's protests came after Angola's Constitutional Court threw out a complaint filed by the runner-up, opposition party UNITA, in the August 24 election.
National Union for the Total Independence of Angola or UNITA, a former rebel group who fought the ruling People's Movement for the Liberation of Angola (MPLA) for nearly three decades, received many of its votes from young people who feel left out of the country's oil riches.
"The citizens are not with the MPLA. We want them out!", demonstrators chanted in unison.
A frustrated youth
Many protestors are young and unemployed who feel failed by the MPLA, some of whose members became billionaires from Angola's oil wealth while most of their countrymen live in poverty.
The demonstrators took over Independence Square, traditionally where the MPLA holds rallies and victory parties.
The protests were peaceful, although analysts fear there is enough anger and youth frustration for them to quickly turn violent.
UNITA's leader Adalberto Costa Junior had called for the protests after losing to incumbent President Joao Lourenco by a few percentage points.
A little more than 51 percent of the electorate voted for the former marxist MPLA while UNITA bagged 44 percent, its best result yet.
UNITA officials have not published any evidence of their claims of electoral fraud.