At least 26 people have been killed in an explosion in the town of Finote Selam in northwestern Ethiopia, amid heavy fighting between government forces and a local militia group.

A further 50 people were injured in Sunday’s blast, according to Manaye Tenaw, CEO of the Finote Selam General Hospital. These victims are only those treated at the hospital, and the total number of casualties is unclear.

Tenaw told CNN that people reported hearing only one explosion, the cause of which is unclear.

The hospital had already treated more than 160 people in the days leading up to the explosion, he added, as fierce fighting between government forces and a local militia known as Fano erupted across the Amhara region earlier this month.

The Ethiopian Human Rights Commission (EHRC) expressed “grave concern” over heavy fighting between the two groups beginning August 3 “following months of tension and sporadic clashes,” it said in a statement Monday.

The Ethiopian government declared a six-month state of emergency in the Amhara region on August 4 after days of clashes.

Once allies against Tigrayan forces in a deadly two-year conflict that ended last November, the government and the Fano militia have fallen out in recent months after the group resisted a move by the federal government to disband regional forces.

Amhara nationalists argue that this would jeopardize regional security.

The EHRC said there was “heavy fighting in and around cities and towns across the Amhara region, which involved the use of heavy artillery resulting in the deaths and injuries of civilians.”

“EHRC has also received credible reports of strikes and shelling including from Debre Birhan, Finote Selam, and Burie resulting in many civilian casualties and damage to residential areas and public spaces,” it said, adding that similar reports were documented in the regional capital city Bahir Dar, as well as its second largest city, Gondar.

The commission also noted “widespread arrest of civilians who are of ethnic Amhara origin,” in the capital city Addis Ababa.

Relative calm has returned to Gondar and Bahir Dar, residents told CNN on Monday. A government spokesperson said cities in Amhara had been “freed” by federal forces, in a televised statement on Friday.

“While heavy fighting has subsided in major urban areas since Augst 9, 2023, it continues in other parts of the region and remains a major concern until a sustainable solution is in place,” said the EHRC.

The United Nations “called on all sides to respect human rights and take steps to deescalate the situation,” noting that “previous states of emergency have been accompanied by violations of human rights” in a statement Friday.

The governments of Australia, Japan, New Zealand, the United Kingdom, and the United States of America also noted civilian casualties, urging all parties to “protect civilians, respect human rights, and to work together to address complex issues in a peaceful manner,” in a joint statement on Friday.

CNN has reached out to the federal government, the Ethiopian National Defense Forces, and the Amhara regional government for comment.

In March, US Secretary of State Antony Blinken said that the US has formally determined that armed forces on all sides of the conflict in northern Ethiopia have committed war crimes.

“After the department’s careful review of the law and the facts, I’ve determined that members of the Ethiopian National Defense Forces, Eritrean Defense Forces, Tigray People’s Liberation Front forces and Amhara forces committed war crimes during the conflict in northern Ethiopia,” Blinken said at a press conference for the release of the State Department’s 2022 Human Rights Report.