A slum in Sierra Leone's capital Freetown was destroyed in a fire late Wednesday, authorities said, adding that the toll was unclear but thousands may have been affected.

"Earlier tonight, the Susan's Bay community was gutted by fire," Freetown City council said in a tweet overnight.

"The extent of the damage is unknown but thousands are likely to have been affected. We will provide more details as we receive them. Keep affected residents in your thoughts and prayers!"

Most homes in Susan's Bay are flimsy constructions of corrugated sheeting and recovered materials.

The community is clustered on Freetown's seafront, close to the city's historic centre.

The European Union's ambassador to Sierra Leone, Tom Vens, said the EU was looking at ways of sending aid to the victims.

"We will reflect with (the) authorities on needed structural measures to reduce risk of such catastrophes re-occurring," he said on Twitter.

The diamond-rich former British colony is one of the poorest countries in the world.

Its economy was ravaged by a 1991-2002 civil war that claimed 120,000 lives, followed by an Ebola epidemic that ran from 2014-16.

Further blows have come from a slump in global commodity prices and the impact of the coronavirus pandemic.