Ethiopian officials said Friday that more than 20 people linked to a prominent rebel group had been arrested after a grenade attack on a police camp that left nine injured.

The attack occurred Thursday evening in the town of Burayu, roughly 20 kilometres northwest of the capital, Addis Ababa, state-affiliated Fana Broadcasting Corporate reported.

The town is located in Ethiopia’s Oromia region, the epicentre of anti-government protests that fuelled the rise of Abiy Ahmed to the post of prime minister last year.

Those arrested so far are either members or supporters of the Oromo Liberation Front (OLF), according to a statement from the Oromia region’s communications office.

“We’ve arrested 22 people who are either members of OLF or sympathisers, and they are suspected of participation in the Burayu grenade attack,” said the statement, which was carried by the state-run Ethiopian Broadcasting Corporation.

The OLF fell out with the ruling Ethiopian People’s Revolutionary Democratic Front (EPRDF) in 1992 and soon began launching armed attacks.

But last year, Abiy removed the OLF from a list of terror organisations, and its exiled leadership made a triumphant return home.

In February, the government announced that some 1,000 OLF members had surrendered their arms and entered rehabilitation camps.

Officials said it was a sign that security issues in the region were being resolved.

OLF leader Dawud Ibsa did not immediately respond to calls and text messages seeking comment Friday.

The injured in Thursday’s attack included one police officer and a female cook at the Burayu camp, Fana said.

All the victims were discharged after receiving medical treatment in Addis Ababa. (AFP)