Kinshasa, DR Congo (AFP) — More than 160 people have died in the worst floods to batter DR Congo's capital Kinshasa in years, UN officials said citing authorities.

After an all-night downpour on Tuesday, major roads in the center of Kinshasa, a city of about 15 million people, were submerged for hours and a key supply route leading to the port of Matadi collapsed.

"As of 16 December, the Congolese authorities reported that at least 169 people have died; around 30 were injured and receiving treatment in hospitals across the city and at least 280 houses were destroyed," the UN Office for the Coordination of Humanitarian Affairs said.

The government has not announced an increased toll since the prime minister's office provisionally put the figure at 120 dead on Tuesday.

The Mont-Ngafula and Ngaliema districts in the capital's west were hardest hit by the torrential rains, according to OCHA, with about 38,000 people affected.

A three-day national mourning period began on Wednesday.

Located on the Congo River, Kinshasa has seen a huge population influx in recent years.

Many dwellings are shanty houses built on flood-prone slopes, and the city suffers from inadequate drainage and sewerage.