Angolan president João Lourenço pledged on Thursday to be "the president of all Angolans" during his inauguration for a second term in the capital, Luanda.
The ceremony took place under a heavy security presence after elections whose results were disputed by the opposition.
The Popular Movement for the Liberation of Angola (MPLA), in power since independence from Portugal in 1975, won the elections held on the 24th of August with 51.17% of the vote, its lowest ever score.
The main opposition party, the National Union for Independence (UNITA), which received 43.95% of the vote according to the electoral commission, claimed to have won the election according to its own count.
The opposition rejected the results and appealed to the Constitutional Court.
The appeal was rejected earlier this month.
Some 15,000 strictly selected Angolans were invited to the ceremony, which was to be attended by some 50 heads of state and government, including Portuguese President Marcelo Rebelo de Sousa.
The MPLA lost the two-thirds majority in parliament, which allowed it to pass laws without the support of another party.