Sudanese warplanes crossed into South Sudan on Tuesday, bombing the town of Khortumbak in Upper Nile State, killing two civilians and injuring others, local officials said.

Maban County Commissioner Peter Alberto told state-owned South Sudan Broadcasting Corporation that civilians were killed on their farms and while walking to a market and aid distribution centre. The attack also destroyed homes and livestock.

“The attack killed two civilians who were working on their farm. It also wounded others,” Alberto said.

Alberto did not provide details on what might have prompted the attack but said he had informed the state governor.

South Sudan People’s Defence Force spokesman, Major General Lul Ruai Koang, described the attack as unprovoked and said the military leadership was aware of the incident.

Koang confirmed the validity of a 2012 non-aggression pact between the two countries.

“That agreement is still valid and from our side, we have not crossed to the side of Sudan,” Koang said.

Landlocked South Sudan took three-quarters of the oil when it became independent in 2011, but the oil moves by pipeline through Sudan, which controls the export facilities.

There has been no statement from the Sudanese military on the matter.