The move could be part of the sanctions that Ecowas – the West African trade bloc – agreed to impose on Niger following the military coup that ousted the elected president Mohamed Bazoum a week ago.
"Since yesterday, Nigeria has disconnected the high-voltage line transporting electricity to Niger," a source at Nigerian Electricity Company (Nigelec) told AFP.
In addition to a one-week ultimatum to restore constitutional order and the suspension of financial transactions with Niger, Ecowas decreed the freezing of "all service transactions, including energy transactions".
"The sanctions will hurt our country very much," Prime Minister Ouhoumoudou Mahamadou said on Sunday on the French TV channel France24.
Niger depends on Nigeria for 70 per cent of its power, buying it from the Nigerian company Mainstream, the company has said. The majority of this power is generated by the Kainji Dam in western Nigeria.
The Nigelec agent indicated that the capital, Niamey, was "supplied thanks to local production". However, 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 180km (110 miles) upstream of Niamey. It is scheduled for completion in 2025, with a targeted annual capacity of 629 gigawatt-hours (GWh).
In addition to the sanctions, Ecowas has also threatened the use of force unless the junta reinstated the elected president of Niger, with one official saying: "The military option is the very last option on the table – the last resort – but we have to prepare for the eventuality."
The new self-proclaimed leader of Niger, General Abdourahamane Tchiani, described the sanctions as "inhumane" and "illegal", and said he would not bow to the pressure the group was exerting.
The ruling military juntas in Mali and Burkina Faso have warned Ecowas against any intervention in Niger, insisting any military action against the new regime would also be tantamount to a "declaration of war" against them.
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.
