One of the two main Darfur rebel groups, the Justice and Equality Movement (JEM), said in a statement it had joined forces with eastern rebels to kidnap the three men who were leaving the government-organised conference in the town of Kassala near the Eritrean border on Tuesday.
"The rebels wanted to kidnap many people from the conference to damage its good work, but the last session finished late so they only managed to kidnap these three members of the state assembly," said the Red Sea state's governor, Hatim al-Wasiyla.
"These three left early at about 11 a.m. (0800 GMT) so they were not in the armed convoy which left after the conference ended at about 4 p.m.," Wasiyla told Reuters.
The convoy, transporting the other delegates, arrived safely in Port Sudan from Kassala.
The three politicians were from the ruling National Congress Party that organised the two-day conference.
Wasiyla said local tribal leaders were in contact with the rebels, who said the three were in good health. But, he said, the rebels had not yet made any demands for their release.
The eastern rebel groups, the Free Lions and the Beja Congress, occasionally clash with government forces.
The Darfur rebels took up arms more than two years ago in the west in fighting that has killed tens of thousands and forced more than 2 million from their homes.
Both sides complain of marginalisation by the government, accusing it of concentrating on the country's central region, where most of the ruling elite hail from. Analysts fear the east has the potential to explode as Darfur has done.