Rebel forces in Ethiopia's northern Tigray region have said they have temporarily withdrawn from the regional capital, Mekelle, as fighting with the national army moves towards the city.

The Tigray People's Liberation Front (TPLF), which has been running the region, said its decision to relocate was made because of concerns about risks to civilians.

Two residents in Mekelle told the BBC that pro-government forces now control the city and TPLF forces have abandoned it. One resident also said mobile phone services appear to have resumed in parts of the city.

The development marks a major shift in the conflict and raises concerns among observers that the fighting could further destabilise the Horn of Africa, potentially drawing in neighbouring countries.

The US Department of State called for "restraint" and "dialogue" on all sides ahead of a diplomatic meeting about the conflict in Egypt on Sunday with leaders from some of Ethiopia's neighbours.

Tigray residents have been trying to recover from a devastating two-year civil war that ended in 2022 when the African Union (AU) brokered a peace deal, known as the Pretoria Agreement, between the two sides.

However, in the last six months there has been a worsening of relations, with both sides accusing each other of violating the agreement.

Last month, the TPLF joined six other armed movements, including the Fano militia from Amhara, to form an alliance whose stated objective is to remove Ethiopia's Prime Minister Abiy Ahmed's government from power.

The civil war was one of the most deadly conflicts this century - the AU's mediator estimated some 600,000 people died as the fighting drove the region to the precipice of famine.

On Friday, neighbours Ethiopia and Eritrea severed diplomatic relations with each other after Addis Ababa accused Asmara of supporting a new rebel alliance - an allegation that it denied.

Ethiopia has also accused Egypt of supporting the rebels, leading to the expulsion of an Egyptian diplomat, which Cairo responded to by ordering an Ethiopian embassy official to leave within the same period.

The United Nations has warned that the deteriorating security situation in northern Ethiopia is severely disrupting humanitarian work and has called on all sides to guarantee safe and unhindered access to people in need.