The UN said two people were killed in eastern Democratic Republic of Congo on the border with Uganda after UN peacekeepers opened fire on Sunday.

UN Secretary-General Antonio Guterres said he was "outraged" by the news and "saddened and dismayed" by the deaths. He demanded "accountability," according to a UN statement.

Videos shared on social media of the incident showed at least one man in a police uniform and another in an army uniform moving toward an unmoving UN convoy behind a closed barrier in the town of Kasindi.

After an exchange of words, the UN peacekeepers appeared to open fire before the gate opened, driving on while continuing to shoot. Onlookers scattered or hid in response.

The representative for North Kivu's governor in Kasindi, Barthelemy Kambale Siva, said that eight people, including two policemen, were seriously injured.

"The government, together with MONUSCO (the UN mission in the Democratic Republic of Congo), have launched an investigation to know the reasons for such crime and obtain severe punishments," government spokesman Patrick Muyaya, said in the statement.

What did the UN mission say?

In a statement, the UN mission said that "soldiers from the intervention brigade of the MONUSCO force... returning from leave opened fire at the border post for unexplained reasons and forced their way through."

The mission added, "This serious incident caused loss of life and serious injuries."

Bintou Keita, special representative of the secretary-general of the UN in Congo, said the suspected perpetrators were arrested, adding that contact had been made with the countries of origin of the soldiers to start the legal proceedings. She did not name the countries.

MONUSCO under pressure

More than 120 different armed groups and factions operate in the eastern region of the Democratic Republic of Congo. The UN's observer mission first deployed in 1999.

In 2010, the mission became the peacekeeping UN Organization Stabilization Mission in the Democratic Republic of Congo, or MONUSCO, with a mandate permitting offensive operations.

Last week, demonstrations against the mission in the eastern cities of Goma and Butembo turned violent as angry locals were protesting the UN peacekeepers' failure to keep the locals safe.

More than 19 people were killed, including three from the UN's mission, during the demonstration, with reports that some of the deaths were due to MONUSCO personnel opening fire on protesters.