Congo's president has held a rare press conference in an apparent response to international condemnation of the violent treatment of Catholic church members and activists protesting his prolonged stay in power.

President Joseph Kabila on Friday called the Central African country's electoral process "firmly engaged" despite a long-delayed vote, and declared that his country was not for sale.

Congolese security forces killed at least six people and injured 68 others on Sunday as thousands of demonstrators held nationwide protests calling for Kabila, whose mandate ended in late 2016, to step down.

The United Nations says excessive force was used.

The U.N. this week also blamed Congolese "state agents" for 1,176 extrajudicial killings last year.

Kabila criticized the U.N. for its slow humanitarian response to deadly violence in the Kasai region.