- About 70 000 people have been affected in the heavy fighting between rebels and pro-government forces.
- Prime Minister Abiy Ahmed sent troops into Tigray last November to oust the region's ruling party.
- A 10-vehicle World Food Programme convoy also came under attack in Afar at the weekend.
At least 20 civilians have been killed and tens of thousands displaced in "heavy fighting" between rebels and pro-government forces in Ethiopia's Afar region, which neighbours war-hit Tigray, an official told AFP on Thursday.
The sustained clashes in Afar highlight the potential for Ethiopia's eight-month-old conflict to expand well beyond Tigray, where thousands of people have already been killed and hundreds of thousands pushed into famine, according to the United Nations.
Tigrayan rebels at the weekend carried out what spokesman Getachew Reda described as a "very limited action" in Afar targeting special forces and militia fighters from the Oromia region, Ethiopia's largest.
But Mohammed Hussen, an official with Ethiopia's national disaster response agency based in Afar, told AFP Thursday the operations were wider in scope and that civilians had been caught in the crossfire.
The heavy fighting is still continuing. So totally about 70 000 are affected directly and they are displaced... More than 20 civilians are dead.
"They (the rebels) are trying to subjugate the Afars. So now the federal forces are joining the Afar special forces, the Afar local communities, the Afar militias. In the last days the Afars were fighting and protecting themselves."
Getachew, the rebel spokesman, dismissed claims Tigrayan rebels had killed civilians as "flat-out lies."
Prime Minister Abiy Ahmed sent troops into Tigray last November to oust the region's ruling party, the Tigray People's Liberation Front (TPLF), a move he said was in response to TPLF attacks on federal army camps.
Though the 2019 Nobel Peace laureate declared victory later that month, TPLF leaders remained on the run and fighting dragged on.
Last month the war took a stunning turn when pro-TPLF fighters reclaimed the Tigray capital Mekele and Abiy declared a unilateral ceasefire.
Yet clashes have continued and officials from six regions and the city of Dire Dawa have since said they would send troops to back up government forces.
- Aid disrupted -
The fighting in Afar has already disrupted aid distribution to Tigray.
A 10-vehicle World Food Programme convoy came under attack in Afar at the weekend, prompting the UN agency to suspend convoys departing from the regional capital Semera.
The route via Semera into Tigray had become critical for aid delivery in recent weeks after two key bridges along other routes were destroyed in late June.
A UN security notice seen by AFP indicated that heavy fighting pitting Afar special forces and federal soldiers against the TPLF took place in Awra and Ewa districts on Wednesday.
Those districts lie east of southern Tigray and northern Amhara, where thousands of militia fighters have been mobilising in recent days.
The road into Ethiopia via Djibouti's port, located east of Afar, is vital for the landlocked country, raising speculation that Tigrayan rebels might try to choke it off.
Mohammed said Thursday the road was "open" and "very safe", adding that any claims to the contrary were TPLF "propaganda".
- Refugee deaths -
Beyond Afar, recent fighting has occurred in western and southern Tigray, disputed territories that were occupied by forces from Ethiopia's Amhara region, which borders Tigray to the south, at the beginning of the war.
Two camps housing thousands of Eritrean refugees have been caught up in hostilities in western Tigray, triggering UN alarm over their safety.
On Thursday the government's Agency for Refugees and Returnees Affairs (ARRA) said at least six refugees were reported to have been killed by TPLF "militants".
The UN had previously confirmed one death.
ARRA accused the TPLF of deploying heavy artillery in the camps, looting vehicles and warehouses and preventing refugees from leaving - creating what is "tantamount to a hostage situation".
Getachew Reda told AFP earlier this week that pro-TPLF forces had no intention of harming refugees.
- Pro-army rally -
In Addis Ababa Thursday, tens of thousands of people joined a rally to show support for the army.
Demonstrators hoisted signs denouncing the TPLF as "Ethiopia's cancer" and proclaiming that the army "stands for truth and justice".
Addis Ababa mayor Adanech Abiebie, whose office organised the rally, said the war "is being wrapped up with victory".
She accused the TPLF of working with foreign media "to defame our army's name".
Demonstrators also criticised alleged meddling by foreign media and diplomats.
"Ethiopia is a sovereign country, and interfering in Ethiopia's sovereignty is forbidden," 39-year-old Abeba Nega told AFP.