A canopy overhanging a stage built for Pope Francis in a Kinshasa stadium collapsed overnight during a heavy storm, Congo authorities said on Monday, three days before he is due to appear there for a public event.

Francis is scheduled to arrive in the Democratic Republic of Congo on Tuesday afternoon and address young people and catechists in the Martyrs' Stadium in Kinshasa, the capital, on Thursday morning.

The canopy was being fixed on Monday, Kinshasa police chief Sylvano Kasongo told Reuters.

"It's the structure and the gyproc (plasterboard) decoration that collapsed but the podium is still in place and work is underway to get everything back in order," he said.

Heavy rain and strong winds are not unusual in Kinshasa.

Pictures posted on social media showed one side of the canopy resting on the stage while the other side was still aloft.

Reporters were not allowed into the stadium on Monday. Troops from the Garde Republicaine, an elite military unit in charge of protecting the Congolese president and state institutions, were guarding it during the repairs.

Interior minister Daniel Aselo Okito visited the stadium on Monday as part of a tour of venues that will host the pope, and said in a statement he expected the repairs to be finished in time for Thursday's event.