Tshisekedi, whose late father Etienne was a veteran of Congolese politics, spoke at a rare rally in Kinshasa that went undisrupted by the government after nearly two years.
“By setting free all political activists who are in prison; they should also allow all politicians who are outside the country to come in freely,” he said.
“My thoughts are with Moise Katumbi, Mbusa Nyamwisi and all others. They should be allowed in the country.”
Katumbi has been living in exile for the last two years and while he has been outside the country, he has been sentenced to three years in absentia over a real estate case.
With the country set to hold its elections two years after they were initially scheduled, Tshisekedi has demanded an all-inclusive election.
Katumbi is a presidential candidate for an opposition coalition called Ensemble.
“To the electoral commission of Congo, Inask them not to proceed with the electronic vote machine,” added Tshisekedi, leader of the Union for Democracy and Social Progress.
“And we want an audit to be carried out on the registration server by an independent body to clear all doubts.”
He dismissed suggestions that he had struck a deal with incumbent president Joseph Kabila to serve as prime minister under his cabinet.