At least 21 people have died after a passenger boat sank in River Nile state in northern Sudan, a medical group has told the BBC.

The boat was travelling between the villages of Tayba al-Khawad and Deim al-Qarai, carrying nearly 30 passengers, including women, elderly people and children, the Sudan Doctors Network said.

"Rescue teams are continuing with their work since there could be more bodies," said Dr Mohamed Faisal Hassan, the network's spokesperson.

Authorities in River Nile state said on Thursday that 21 bodies had been recovered, AFP news agency reported.

Eyewitnesses said the boat capsized due to high waves on Wednesday evening in the Shendi area.

In an earlier statement, the medical group said six people had survived.

The group urged authorities to deploy specialised rescue teams and equipment to accelerate search efforts.

It urged authorities to "take immediate measures to ensure river transport safety and prevent the recurrence of such disasters that claim innocent lives".

"This painful humanitarian tragedy once again reveals the fragility of river transport and the absence of basic safety requirements," it added.

Dr Hassan told the BBC that weak regulation of river transport may have contributed to the tragedy.

He said many of the boats operating on the Nile were privately owned and that authorities lacked proper regulatory systems and safety measures.

Authorities did not immediately respond.

Sudan often sees accidents involving traditional boats, which are commonly used to cross the Nile because bridges are scarce, particularly in rural areas.

The country has been engulfed in a brutal conflict since April 2023, when fighting erupted between the Sudanese army and the paramilitary Rapid Support Forces (RSF).

The war has devastated large parts of the country, particularly the capital Khartoum and regions such as Darfur, displacing millions and crippling basic services.

River Nile State, where the boat accident occurred, has been largely spared from frontline fighting, though the broader instability has strained resources and infrastructure nationwide.