Twenty-two people have been arrested in connection with a recent grenade attack, Ethiopia’s Oromia regional state administration said on Friday.

The 22 are accused of involvement in the grenade attack on Thursday evening in Burayu town, on the outskirts of Ethiopia’s capital city, Addis Ababa, the Oromia regional communication bureau said in a statement.

Nine police officers were injured in the grenade attack targeting a police station.

The 22 suspects are also accused of having connections to rebel group Oromo Liberation Front (OLF), the statement said.

Oromia regional state, located in central Ethiopia, is home to some 40 percent of the country’s total population of about 105 million.

In recent months, the southern and western parts of Oromia regional state have been suffering from insecurity, with the Ethiopian government putting the blame on forces affiliated to the OLF.

The OLF is an armed group claiming to fight for the rights of ethnic Oromos who make up about 35 percent of Ethiopia’s population.

An estimated 2,800 OLF fighters are based mainly in the western and southern parts of Oromia regional state, the principal operating ground of the OLF.

The OLF was designated as a terrorist group by the Ethiopian parliament in 2011. It was removed from the terror list in July 2018 to help facilitate negotiations and foster reconciliation.