An Egyptian comedian has sparked anger by using blackface in a sketch and mocking Sudanese people, drawing attention to what experts say is a deeper racism problem in the region.

Speaking Sudanese Arabic and wearing blackface, Shaimaa Seif chatted to Egyptian commuters on a bus as part of a sketch aired on the programme "Shaklabaz".

The footage was broadcast by the local affiliate of Saudi-funded MBC, one of the largest entertainment channels in the region, and offended many in the Sudanese community who voiced their anger online.

There have been calls to boycott MBC, but neither the broadcaster nor Seif have apologised for the sketch since it was aired on May 10.

"Was this supposed to make us laugh? While you were filming we were protesting with the people," said Marwa Babiker, a Sudanese doctor with a sizeable social media following.

She was referring to unprecedented mass protests in Sudan that led to the ouster last month of longtime ruler Omar al-Bashir.

Others turned to social media to criticise negative portrayals of Sudanese people, just the latest such incident involving Egyptian entertainers.

In December, Bushra, a well-known actress and singer, released a video clip showing a man in a black mask.

And during Ramadan last year, comedian Samir Ghanem and his daughter sported fake dreadlocks and darkened their skin for a TV series.

Eve Troutt-Powell, a Middle East history professor at the University of Pennsylvania, said blackface has "been a trope in Egyptian entertainment for over a century."

"There is a larger history at play behind the racist caricatures of black people in Egypt and other parts of the Middle East as well, and that is the history of slavery," said Troutt-Powell.

Arab traders sold millions of Africans as slaves from the ninth century, a past which continues to impact race relations throughout the Middle East.

The Arabic word for slave, abed, is commonly used as a derogatory racial epithet.

'Fixation on skin tone'

Egypt has been bold in its political and economic push towards countries in sub-Saharan Africa, but that has not prevented racist outbursts by its diplomats.

An Egyptian official was in 2016 accused of calling African diplomats "dogs and slaves" at a United Nations conference in Kenya.

Mona Kareem, a research fellow at the Forum Transregionale Studien in Berlin, explained such slurs are rooted in the idea of "blackness as something to fear or ridicule".

"A fixation on skin tone is only an expression of... racial bias, and does not capture the complexity of the racial experiences that blacks have had in the Arab world," she told AFP.

"Many of these representations (on television) give voice to already-existent racial images and myths," Kareem added.

Several human rights groups have criticised pervasive racism and obstacles to local integration for non-Egyptians of African descent in the country, as well as in other Arab nations such as Lebanon.

In Western countries where blackface was a common practice during the 19th and 20th centuries, such as the Netherlands and the United States, incidents of its modern-day usage spark outrage.

Yet despite vigorous online debates in the Arab world, critics of blackface have not been as effective in changing attitudes towards Arabs of African descent and sub-Saharan Africans.

"It seems, particularly in comedy, that a clear-eyed and heartfelt discussion of political and racial history still needs to take place in Egyptian society," said Troutt-Powell.

"And it must also continue in other societies."