Three humanitarian workers, belonging to the Sudanese Red Crescent Society, were killed on Sunday in Sudan's Blue Nile state.

"A heinous attack on Sunday targeted a group of humanitarian workers belonging to the Sudanese Red Crescent Society as they were returning from al-Kurmuk town in Blue Nile state after completing a humanitarian mission," Sudan's Humanitarian Commissioner Ahmed Mohamed Adam announced in a statement Sunday.

"The attack resulted in the killing of three workers of the group," he said.

Adam condemned what he described as "unjustified attack" which targeted people who dedicated themselves to helping the needy, adding that the attack "contradicts the religious teachings and norms of the Sudanese community."

He further urged the armed groups to respect the international humanitarian law and the principle of protecting the humanitarian workers.

There has been no claim of responsibility for the attack so far.

The Blue Nile state has been witnessing armed clashes between the Sudanese army and fighters of the Sudan People's Liberation Movement (SPLM)/northern sector since 2011.