Eritrea's capital came under fire from Ethiopia's breakaway Tigray region Friday, raising fears that Ethiopia's internal conflict could spread as leader Abiy Ahmed resisted calls for dialogue.

For more than three weeks now, Ethiopia and Tigray have engaged in fierce fighting that the International Crisis Group said Friday had left thousands dead "including many civilians as well as security forces".

Ethiopia and the region of Tigray
Ethiopia and the region of Tigray AFP / Jean-Michel CORNU

On Friday night, at least one rocket fired from the northern Tigray region targeted neighbouring Eritrea, four regional diplomats told AFP.

Abiy, the winner of last year's Nobel Peace Prize, announced Thursday a "third and final phase" in his campaign against leaders of the Tigray People's Liberation Front (TPLF).

Ethiopian troops on a road near the Tigrayan city of Humera
Ethiopian troops on a road near the Tigrayan city of Humera AFP / EDUARDO SOTERAS

Global concern remains centred on the half a million residents of Mekele, Tigray's regional capital, which the army says it has encircled ahead of the threatened attack.

World leaders and human rights groups have warned such a strike could violate rules of war and were calling for urgent mediation.

Pope Francis was among those worried about the intensifying fighting, growing loss of life and displacement, Vatican media head Matteo Bruni said Friday.

A blood-stained sandal lies next to the grave of an alleged victim of a massacre that unfolded in the Tigrayan town of Mai Kadra November 9
A blood-stained sandal lies next to the grave of an alleged victim of a massacre that unfolded in the Tigrayan town of Mai Kadra November 9 AFP / EDUARDO SOTERAS

Abiy announced military operations in Tigray on November 4 after months of friction between his government and the TPLF, which dominated Ethiopian politics for nearly three decades before Abiy took office in 2018.

The prime minister has refused to negotiate with the TPLF and dismissed calls for dialogue as "interference" in Ethiopia's internal affairs.

A youngster in Bahir Dar, the capital of Amhara region, stands in front of a wanted sign showing members of the Tigray People’s Liberation Front (TPLF), who are being sought for alleged treason
A youngster in Bahir Dar, the capital of Amhara region, stands in front of a wanted sign showing members of the Tigray People’s Liberation Front (TPLF), who are being sought for alleged treason AFP / EDUARDO SOTERAS

On Friday he met with three African ex-leaders -- Joaquim Chissano of Mozambique, Ellen Johnson Sirleaf of Liberia and Kgalema Motlanthe of South Africa -- dispatched this week by the African Union as mediators.

A medic disinfects tools at a medical facility in Um Raquba, a camp that has been set up for Ethiopian refugees in eastern Sudan
A medic disinfects tools at a medical facility in Um Raquba, a camp that has been set up for Ethiopian refugees in eastern Sudan AFP / ASHRAF SHAZLY

In a statement issued after their meeting in Addis Ababa, Abiy said he appreciated "this gesture and... the steadfast commitment this demonstrates to the principle of African solutions to African problems".

Even so, the government has a "constitutionally mandated responsibility to enforce rule of law in the region and across the country," his office said in a statement.

Unrest continues in Ethiopia in the wake of a massacre of hundreds of civilians in the Tigray region in the north of the country, as conflict continues between government forces and the Tigray People's Liberation Front
Unrest continues in Ethiopia in the wake of a massacre of hundreds of civilians in the Tigray region in the north of the country, as conflict continues between government forces and the Tigray People's Liberation Front AFPTV / Solan KOLLI

"Failure to do so would further a culture of impunity with devastating cost to the survival of the country," it said.

UN chief Antonio Guterres welcomed the talks with the AU envoys and urged all parties to "peacefully resolve the conflict".

The UN Secretary-General also stressed the need "to ensure the protection of civilians, human rights and access for humanitarian assistance to the affected areas".

Ethiopian refugees walk through a transit centre at the Sudanese border town of Hamdayit on Thursday.Over 43,000 refugees have crossed into Sudan since fighting broke out in Tigray on November 4, the UN says
Ethiopian refugees walk through a transit centre at the Sudanese border town of Hamdayit on Thursday.Over 43,000 refugees have crossed into Sudan since fighting broke out in Tigray on November 4, the UN says AFP / ASHRAF SHAZLY

The Tigrayan government, meanwhile, said Friday the federal army was bombarding towns and villages and inflicting heavy damage, although it did not specifically mention Mekele.

"Our struggle will continue from every direction until the self-determination of the People of Tigray is guaranteed and the invading force is driven out," Tigrayan authorities said in a statement read on regional television.

A communications blackout in Tigray has made it difficult to verify claims from both sides on the fighting.

Hostilities have erupted in a year when the 55-member AU -- which is headquartered in Addis Ababa -- resolved to play a more prominent role in resolving conflicts across the continent under the slogan "Silencing the Guns".

At least one rocket fired from Tigray targeted neighbouring Eritrea Friday night, four regional diplomats told AFP, the second such attack since Ethiopia's internal conflict broke out earlier this month.

There was no immediate confirmation of how many rockets were fired, where they landed, and any casualties or damage caused.

The TPLF has accused Ethiopia of enlisting Eritrean military support in the fighting, a charge Ethiopia denies.

The group claimed responsibility for similar strikes on Eritrea two weeks ago, but there was no immediate comment from its leaders Friday.

Abiy, who ordered the "final" offensive on TPLF forces in Mekele after the lapsing of a deadline for their surrender earlier this week, said "great care" would be taken to protect civilians and spare the city from severe damage.

The prospect of a full-scale attack accelerated diplomatic efforts this week to resolve the conflict, with the UN Security Council holding its first meeting on Tigray and US and European officials urging restraint.

French Foreign Minister Jean-Yves Le Drian, who met his Ethiopian counterpart Demeke Mekonnen in Paris on Thursday, called for urgent measures to protect civilians as the humanitarian fallout from the crisis worsened across the region.

The UNHCR said Friday that nearly 100,000 Eritrean refugees in Tigray could run out of food as early as Monday if supplies could not reach them.

In eastern Sudan, meanwhile, where more than 40,000 refugees have escaped the fighting in Tigray, local authorities are struggling to meet the sudden surge in demand for food, shelter and other life-saving essentials.