Authorities arrested Mohammed Mokhtar al-Khatib, secretary general of the opposition Sudanese Communist Party, and another party leader on Thursday after they returned from a visit to South Sudan, a party official said.
On Wednesday, the party said the men were detained in Juba after meeting Sudanese rebel leaders.
(Reporting by Khaled Abdel Aziz,; Writing by Lilian Wagdy, Editing by Angus MacSwan)