Large parts of Malawi have been plunged into darkness as water levels at the country’s main hydro power plant fell to critical levels due to a severe drought, according to its electricity company.

The impoverished southern African country which relies on hydroelectricity has been hit by intermitted blackouts since last year, but the outages have recently worsened, lasting up to 25 hours.

The state-owned Electricity Supply Corporation of Malawi (Escom) said on Thursday that power output had been halved as water levels in the Shire river dropped to critical levels.

The water from the river normally generates a total of 300 megawatts of electricity, which is 98% of the country’s supply. “For the past three weeks, the available capacity was 160 megawatts,” said Escom said in a statement.

Affected areas include large parts of the capital Lilongwe and in the second city of Blantyre.

A number of businesses and hospitals in the country had been forced to use diesel-powered generators to keep the lights on.

According to the World Bank, only 8% of Malawi’s 17 million people have access to electricity.