Dozens of people have died after Sudan’s military cracked down on a protest camp earlier in the week.
An opposition politician has been detained in Sudan after meeting Ethiopia’s prime minister, his party has said.
Mohammad Esmat was part of a delegation holding talks with Abiy Ahmed, who flew in from Addis Ababa on Friday.
No further details were given about his arrest.
His visit follows the deaths of dozens of people when troops stormed a protest camp on Monday following long demonstrations against military rule.
Mr Ababa held discussions with both the Transitional Military Council (TMC), and the opposition Declaration of Freedom and Change Forces (DFCF) alliance.
As he tried to mediate, Mr Ahmed urged both sides to exercise “bravery” in resolving their standoff.
He arrived in Sudan the day after the African Union – based in Ethiopia – suspended Sudan, backing the opposition’s demand for civilian rule.