Sudan's Darfur region is facing a growing risk of genocide as the world's attention is focused on conflicts in Ukraine and Gaza, a UN expert warns.

"We do have circumstances in which a genocide could be occurring or has occurred," the UN Special Adviser of the Secretary-General on the Prevention of Genocide, Alice Wairimu Nderitu, told BBC's Newsday programme.

She said many civilians were targeted based on their ethnicity in Sudan's besieged city of El Fasher, where fierce fighting has intensified in recent days.

More than 700 deaths have been reported in 10 days by a medical charity in the city.

El Fasher is the last major urban centre in the Darfur region that remains in the hands of the Sudan's army.

The military has been fighting the paramilitary Rapid Support Forces (RSF) for more than a year, in a civil war that has killed thousands and forced millions from their homes.

The situation is unfolding to a "Rwanda-like" genocide of 1994, Ms Nderitu said, citing a UN analysis on the increasing risk factors.

"Increased hostilities in El Fasher have now opened a really alarming chapter in this conflict," she added.

"I'm calling for attention to this particular conflict. I have been trying to get my voice out but my voice is drowned out by other wars - in Ukraine and Gaza."

Similar fears of a possible genocide in Darfur were expressed by Human Rights Watch (HRW) recently.

A report from the campaign group said ethnic cleansing and crimes against humanity had been committed against ethnic Massalit and non-Arab communities in the region by the paramilitary forces and its Arab allies.

It called for sanctions against those responsible for the atrocities, including the RSF leader, Mohammed Hamdan Dagalo, widely known as Hemedti.

The current violence has erupted out of a long history of tensions over resources between non-Arab farming communities, including the Massalit, and Arab pastoralist communities.

The BBC has heard from residents about the climate of fear and death as the conflict rages with no end in sight.

The internet has been cut making access to the city difficult, as soldiers from the RSF group continue to besiege the city.

The UN says about 15,000 people are feared to have been killed in the West Darfur city of El Geneina last year.

Last June, West Darfur Governor Khamis Abakar was killed hours after accusing the RSF of committing genocide. He is the most senior official known to have been killed since the conflict began in April.

The RSF says it is not involved in what it describes as a "tribal conflict" in Darfur.

The paramilitary group emerged from the Janjaweed militia which was accused of genocide and ethnic cleansing against non-Arab communities in Darfur in 2003, after rebels took up arms, accusing the government of ignoring the region.