Ethiopia’s prime minister has given forces in the northern region of Tigray 72 hours to surrender as government troops advance on the capital, Mekelle.

Abiy Ahmed told Tigrayan leaders they were “at a point of no return”.

The Tigray People’s Liberation Front (TPLF), which controls the mountainous region, has vowed to keep fighting.

The conflict has reportedly killed hundreds and displaced thousands in recent weeks. The UN has warned it could trigger a humanitarian crisis.

Earlier the Ethiopian military warned Mekelle’s 500,000 residents that the city would be encircled by tanks and subjected to artillery fire.

“There will be no mercy,” a spokesman said.

TPLF leader Debretsion Gebremichael told Reuters news agency that his forces had managed to stall advancing federal troops.

“They [are] sending waves after waves but to no avail,” he told Reuters news agency.

The government said its troops took over some key towns last week. However, information is difficult to confirm and claims cannot be independently verified because phone and internet connections have been down since the beginning of the conflict.

In a statement on Sunday aimed at the TPLF leadership, Mr Abiy said: “Your journey of destruction is coming to an end, and we urge you to surrender peacefully within the next 72 hours, recognising you are at a point of no return. Take this last opportunity.”

Mr Abiy said TPLF forces should “surrender peacefully” and that the population of Mekelle should support government forces “in bringing this treasonous group to justice”.

On Friday, South Africa’s President Cyril Ramaphosa, in his capacity as the African Union chairman, announced the appointment of three former presidents to broker talks to end the conflict.

But Ethiopia has rejected the offer because it sees the operation as an internal “law enforcement” mission.

“We don’t negotiate with criminals... We bring them to justice, not to the negotiating table,” Mamo Mihretu, a senior aide to Mr Abiy, told the BBC.

“Our African brothers and sisters would play a more significant role if they put pressure on TPLF to surrender and for that, you know, nobody needs to go to Tigray or Mekelle to make that point clear to them.”

Mr Mamo said that former leaders from Mozambique, Liberia, and South Africa – who are due to arrive in the country in the coming days – would not be able to visit Tigray because of the ongoing military operation.

Communication and transport services has been severely hampered since fighting broke out.

Mr Mamo said that the government was doing its “utmost” to allow UN agencies to provide assistance to people in Tigray. (BBC)