Tensions have been simmering in recent days in Port Sudan where anti-government protesters have reportedly blocked roads over rising insecurity.

Local media have linked the unrest to rejection by the Hedendoa tribe of an October peace deal between rebel groups and the Sudanese government.

Hadendoa, the largest subdivision of the Beja people in the region, fear their tribe will be under-represented in regional legislative and executive bodies under the Juba agreement.

Saturday's blast took place late in the evening at a busy sporting club in Port Sudan, the provincial capital of the Red Sea state, and also involved an armed attack.

"An explosive device went off at Al-Amir club... killing four people," the Central Committee of Sudan Doctors said in a statement.

Three others were wounded after being shot or stabbed, it added.

Witnesses said the attack was carried out by unidentified armed men on a motorcycle but it was not immediately clear what motivated it.

Authorities in the Red Sea state said in a Sunday statement that one of the perpetrators had been arrested.

Dozens of people later gathered outside the public prosecutor's office in Port Sudan demand the assailants be brought to justice, witnesses said.

Saturday's explosion was the latest in a series of violent incidents in Port Sudan, including an attack Friday by unidentified assailants on security forces.

On Saturday a man was killed during a fight on a public bus and that same day there was a failed bid to attack a hotel with explosive, authorities said.

A government statement said that five people were killed on Saturday alone, while six others were wounded in recent unrest.

The doctors' committee, an independent union of medics, blamed "tribal strife" for the violence and urged security forces to step in.

Sudan has been led by a transitional civilian-military administration following the April 2019 ouster of Islamist president Omar al-Bashir, who ruled Sudan with an iron fist for 30 years.

The country has since been undergoing a rocky period marked by a wrenching economic crisis and deepening political division.