U.N. officials report as many as 20 people are feared dead in Kinshasa, after violence broke out during demonstrations calling for longtime President Joseph Kabila to step down after his term in office expired Monday.
Three deaths have been confirmed by VOA Afrique.
Residents in some parts of Congo's capital blew whistles at midnight to signal that it was time for Kabila to leave. Gunfire that was heard in several districts continued Tuesday.
Monday, protests took place in several neighborhoods in Kinshasa, despite a ban on demonstrations and a large military presence. Witnesses say police fired tear gas to disperse the protesters.
Much of the capital was deserted, with shops closed and people staying home fearing violence.
In the eastern city of Goma, human rights groups say dozens of protesters were arrested. The United Nations expressed concern over the "wave of arrests" in the past three days, calling many of them arbitrary.
Congolese opposition leader Etienne Tshisekedi said Tuesday people should not recognize the "illegal and illegitimate authority" of President Kabila, whose term in office expired without him stepping down and with no elections in sight.
In a YouTube video, Tshisekedi urged people to "peacefully resist" what he said was a coup d'etat backed by the country's constitutional court.
The court has ruled that Kabila can remain in power until new elections are held. The ruling party has proposed a vote take place in April 2018.
Presidential adviser Barnabe Kikaya said it was unconstitutional to demand that Kabila step down at midnight.
"The constitution clearly states that the president remains in his position until his successor is elected by the people of the Congo, not by a loud and insistent mob,'' Kikaya said.
The government says elections scheduled for this November had to be postponed because of logistical and financial challenges.
Kabila has been president of the DRC since his father was assassinated in 2001. He won elections in 2006 and 2011 in polls the opposition claims were rigged. He is barred by the constitution from seeking a third term.
Congo has never had a peaceful transfer of power since independence from Belgium in 1960. Observers fear the current political crisis could trigger a repeat of civil wars that killed millions of people between 1996 and 2003.