WASHINGTON/BRUSSELS — The United States on Monday expressed concern over "reports" about Tigray People's Liberation Front (TPLF) taking over of Dessie and Kombolcha, in the disputed region of Tigray in northern Ethiopia.

"Continued fighting prolongs the dire humanitarian crisis in northern Ethiopia," US Secretary of State Anthony Blinken said in a tweet. "All parties must stop military operations and begin ceasefire negotiations without preconditions," he stressed.

Meanwhile, the European Union (EU) Monday called on all parties in Ethiopia to stop fighting and urged the African Union to host ceasefire negotiations. "All parties must stop the fighting in northern Ethiopia, lift the blockade for humanitarian aid, and refrain from hate speech," tweeted EU High Representative Josep Borrell.

Borrell added, "African Union Olusegun Obasanjo is best placed to host ceasefire negotiations without preconditions." Obasanjo, a former President of Nigeria, was appointed as the African Union's High Representative for the Horn of Africa in August.

The situation in Ethiopia was grim as fighting between the government forces and the TPLF escalated with Ethiopia's Prime Minister Abiy Ahmed has appealed to citizens to take up arms to block advancing rebel fighters.

He made the call on Facebook after the rebels, from the northern Tigray state, reportedly seized control of more towns in neighboring Amhara. The US has called for a ceasefire in a yearlong conflict that has created a humanitarian crisis. The TPLF says its aim is to break a siege of the northern region.

In his statement on Sunday, Abiy said the rebels' advance was "pushing the country to its demise". He urged citizens to "organize and march through [any] legal manner with every weapon and power... to prevent, reverse and bury the terrorist TPLF", according to a translation on the Addis Standard news site.

On Saturday, Washington expressed "deep concern" about the expansion of fighting in Tigray region, and called on the TPLF to withdraw from the Amhara and Afar regions and stop its progress in Dessie and Kombolcha, spokesperson of US Department of State Ned Price said.

US repeatedly stressed no military solution to the conflict in the Tigray region, calling on the conflicting parties to negotiate without preconditions.

In a tweet on Monday, the Ethiopian government said the rebels "summarily executed more than 100 youth residents" in the Kombolcha area. The TPLF has not commented and there has been no confirmation of the killings.

It has been difficult to verify claims made by both sides in the conflict because communications have been restricted. Thousands of people have been killed in the war, millions displaced and hundreds of thousands are facing famine conditions, the UN says.

Both sides of the conflict have also been accused of committing atrocities, but they both deny the allegations. The war broke out on Nov. 4 last year, when Abiy ordered a military offensive against regional forces in Tigray.

He said he did so in response to an attack on a military base housing government troops there. The escalation came after months of feuding between Abiy's government and leaders of the TPLF, which was the dominant political party in Tigray.

The authorities later labeled the TPLF a terrorist organization and ruled out any peace talks with them. The federal government's renewed ground offensive in recent weeks, including using airstrikes has failed to halt the rebels' territorial gains. — Agencies