President Tshisekedi said the torrential rains are as a consequence of climate change.
The death toll from floods caused by torrential rains in the Democratic Republic of Congo’s capital Kinshasa has risen to 141, the government has said.
Videos showing the lifeless bodies of victims of the heavy rains have gone viral in Kinshasa.
Over 38,000 houses were flooded while 280 others collapsed following the floods.
President Félix Tshisekedi, who is in the United States for the US-Africa summit, declared three days of national mourning starting Wednesday December 14.
President Tshisekedi said the torrential rains are as a consequence of climate change.
"This should have been avoided if the commitments of the polluting countries had been respected for more than 13 years."
The Deputy Prime Minister in charge of Security and Interior Daniel Aselo said that illegal structures in the city will be demolished and people who live in them relocated elsewhere.
"The governor of the city of Kinshasa has been instructed to identify all these sites (illegal structures) and this should be done as soon as possible," said Mr Aselo.
Kinshasa, a city of about 15 million people, is experiencing exponential urbanisation with tragedies being experienced every rainy season as a result of floods.
"This [latest] tragedy calls for a collective awareness of the urgent need to respect urban planning rules by refraining from building on so-called non-aedificandi sites (places where structures should not be built), from throwing rubbish into rivers and gutters, whose role is to drain rainwater and not to receive any kind of rubbish," Kinshasa Governor Gentiny Ngobila wrote in his communiqué.
"It is when we unfortunately have these anarchic constructions that we suffer these types of setbacks that cause a lot of damage," said Prime Minister Sama Lukonde.
Former Katanga governor Moïse Katumbi called for the punishment of those found negligent in the management of the city.
"The absence of gutter cleaning and water drainage has turned some neighbourhoods into cemeteries," he said.
The government said that Highway 1, which has been destroyed by the floods preventing movement of commercial traffic taking foodstuffs to Kinshasa, must be repaired quickly. The Prime Minister has already announced that work to repair the road to allow the capital to get supplies as the festive season approaches has started.
He said that movement of traffic on the road could resume in four days.