The water utility in Angola's capital vowed Friday to repair a burst water main within days, to end severe shortages that have lasted a week across much of Luanda.

Residents have to trek long distances to find water, which is so scarce that prices have doubled this week due to the shortage, jumping from 7,000 to as much as 14,000 kwanzas ($70 to $140) for a cistern full.

The increase was even steeper for 25-litre containers, soaring from 20 to 50 kwanzas in some neighbourhoods.

"The shortage is due to a maintenance problem in an aqueduct serving the capital... worsened when a construction company ruptured a main," said water utility Epal's spokesman Domingos Pacienca.

"Epal is is doing everything possible to repair the damaged main so that the people won't suffer shortages," he added, vowing to restore the system to normal by Sunday.

Normal is especially relative in this city of seven million, where most people live without running water or electricity.

The UN children's agency UNICEF estimates that 87 percent of the urban population lives in shacks, even though the nation's oil riches have given Angola one of the world's fastest-growing economies.