JUBA (Reuters) -South Sudanese authorities have suspended access to social media platforms for a minimum of 30 days after videos depicting the alleged killings of South Sudanese nationals in Sudan's El Gezira state triggered riots and deadly revenge attacks.

The block was to be implemented at midnight on Wednesday, Napoleon Adok, director general of the National Communications Authority, wrote in a letter dated Wednesday to internet service providers.

"This is culminating from the recent upheaval in Sudan, that has exposed the South Sudanese population to unprecedented levels of extreme violence through social media posts," Adok wrote in the letter seen by Reuters.

Customers of mobile operators MTN South Sudan and Zain would not be able to access Facebook, TikTok and other platforms for a maximum period of 90 days, the companies said in statements issued on Wednesday.

A Reuters reporter in Juba was unable to access Facebook or TikTok.

At least 16 Sudanese nationals were killed last week when riots erupted in South Sudan's capital Juba and elsewhere in the country.

Youths in several cities looted and vandalised shops owned by Sudanese nationals and burned several homes, police said, in retaliation for what they believed was the involvement of Sudan's military and allied groups in the killings in El Gezira.

The Sudanese army has condemned what it called "individual violations" in El Gezira.

"The effect is a bit huge because as an artist, I depend so much on social media," said Isaac Anthony Lumori, also known as Mc Lumoex, a popular South Sudanese musician and founder of a comedy show.

"My message to the government is to seek an amicable way of solving this issue, especially engaging the government of Sudan to make sure that (their) army does not misbehave to the extent of taking human life," he told Reuters.

(Writing by Hereward Holland; Editing by Raju Gopalakrishnan, Tannur Anders and William Maclean)