Seven people were killed and 28 others injured at the weekend after Angolan police foiled a protest in Lunda Norte province, 656 km north of the country's capital Luanda.
The incident took place in Cafunfu village, Cuango municipality.
Police said in a statement on Saturday that it foiled an armed rebellion organised by the Lunda Tchokwe Protectorate Movement's (LTPM), which resulted in the death of some demonstrators.
They said the demonstrators wanted to attack a police station in order to raise the movement's flag.
LTPM's head José Mateus Zecamutchima denied that it was an armed rebellion, saying they held a peaceful and orderly demonstration aimed urging the government to meet them to dicsuss the region's autonomy.
"The killing of seven demonstrators and the injuring of 28 others is a barbarous and coward act," he said.
LTPM is a political group set up in 2007. It is seeking administrative and financial autonomy of the former Tchokwe Kingdom, which comprises provinces of Lunda Norte, Lunda Sul, Moxico and Kuando Kubango.
Angola has extensive diamond reserves (estimated at 180 million carats), especially in the provinces of Lunda Norte and Lunda Sul in the north-eastern parts of the country.
In 2007, the group sent its manifesto to the then President José Eduardo dos Santos calling for discussion of the region's autonomy. They did not receive feedback.
In 2017, the US Department of State in its Country Reports on Human Rights Practices: Angola said members of the LTPM held several protests during that year demanding autonomy.
The government at times arbitrarily restricted the activities of associations it considered subversive by refusing to grant permits for organised activities, it added.