Nigeria has cut its electricity supply to Niger after West African neighbours imposed sanctions on the junta that ousted the country's elected leader last week, a Niger power company source said on Wednesday.

"Since yesterday, Nigeria has disconnected the high-voltage line transporting electricity to Niger," a source at Niger's power company Nigelec told AFP.

Niger depends on Nigeria for 70 percent of its power, buying it from the Nigerian company Mainstream, according to Nigelec, the country's monopoly supplier.

The electricity is generated by the Kainji Dam in western Nigeria.

The capital Niamey has a local production source, but many districts suffered from frequent power cuts even before the coup.

Niger is hoping to achieve energy independence by building the Kandadji Dam on the Niger River, about 180 kilometres (110 miles) upstream from Niamey.

It is scheduled for completion in 2025, with a targeted annual capacity of 629 gigawatt-hours (GWh).

Niger is one of the poorest countries in the world, frequently ranking at the bottom of the UN's Human Development Index, a benchmark of prosperity.

"The sanctions will hurt our country very much," Prime Minister Ouhoumoudou Mahamadou said on Sunday on the French TV channel France24.