Belgium's King Philippe has decried the racism meted out in the Democratic Republic of Congo under the colonial rule of his ancestors.
"This regime was one of unequal relations, unjustifiable in itself, marked by paternalism, discrimination and racism," he said.
King Philippe is on a week-long visit to DR Congo at the invitation of President Félix Tshisekedi.
The king was speaking in the grounds of DR Congo's parliament in Kinshasa.
"On the occasion of my first trip to Congo, here, in front of the Congolese people and those who still suffer from it today, I wish to reaffirm my deepest regrets for these wounds of the past," the 62-year-old monarch said.
Belgium's colonial record in DR Congo was one of the bloodiest in Africa.
Why was Belgium's colonial rule so brutal?
- Belgium controlled the vast, mineral-rich central African country, which is 77 times its size, from the 19th Century until independence in 1960
- The entire country was initially declared to be the personal property of King Leopold II
- More than 10 million Africans are thought to have died during his reign from disease, abuse, and while working on plantations for him
- Authorities would chop off the limbs of enslaved people when they did not meet quotas of materials such as rubber demanded by the crown
Earlier on Monday King Philippe handed over a giant Congolese mask, one of about 84,000 artefacts taken during the colonial era which Belgium has agreed to return.
The mask, called Kakuungu, was previously exhibited at Belgium's Royal Museum for Central Africa.
The newly returned mask was used during healing ceremonies by the Suku community, from the south-west of the country.
It was bought by an art dealer 70 years ago before being exhibited at the Belgian museum. It is not clear how it came into the dealer's possession from the Suku people.
King Philippe said the object was on "indefinite loan" to DR Congo.
It is currently not legally possible for Belgium to donate objects from a federal collection, according to Belgian news site, vrt news.
"I wanted, during our visit at the National Museum and in your presence, to return to you this exceptional work in order to allow Congolese to discover and admire it," the king said.
"It marks the symbolic beginning of the reinforcement of the cultural collaboration between Belgium and Congo," he continued.
Many more artefacts are to be returned from the Royal Museum for Central Africa, nearly 70% of whose art objects were seized during the colonial period.
After the handover an agreement was signed to open cultural collaboration between DR Congo's National Museum and the Royal Museum for Central Africa, but the details have not been made public.
King Philippe's aunt, Princess Esmerelda told the BBC it was right that the looted objects were returned.
"Former European colonial powers should own up to the past," she told the BBC's World Tonight programme.
"I strongly believe that artefacts that were stolen from so many countries in Africa and elsewhere should go back to where they belong."
Millions of Congolese suffered acts of cruelty under colonisation, particularly during the reign of King Leopold II, who owned the Congo Free State as his personal property.
Wednesday's expression of regret over colonisation was not King Philippe's first olive branch.
In 2020, he wrote to President Tshisekedi on the 60th anniversary of the country's independence expressing his "deepest regrets" for the colonial abuses committed under his ancestors.
But Princess Esmerelda said more was needed: "I feel that probably the apologies should be coming soon, formal apologies for the past and for the colonial atrocities that were committed".
King Philippe's week-long visit, his first since ascending the throne in 2013, has received a mixed reception from people the BBC spoke to in Kinshasa.
"I'm very happy about this visit, because the country has been going badly since the Belgians left," one person said.
While another was less enthusiastic: "The president decides to invite the Belgian king, to do what, to loot us again?"
As part of the trip, King Philippe also met Corporal Albert Kunyuku, the last surviving Congolese World War II veteran who fought alongside the Belgians. At a memorial of former fighters a wreath was laid, and King Phillipe presented Corp Kunyuku with a medal.