Moise Katumbi, the opposition presidential hopeful in the Democratic Republic of Congo, has flown to South Africa for medical treatment, his lawyer says, a day after authorities issued an arrest warrant for him.
He was accused of hiring foreign mercenaries in an alleged plot against the state, which he denies.
Mr Katumbi's lawyer said he had been in hospital since police had fired tear gas during a protest.
Elections are due in November.
Prosecutors allowed him to travel for treatment on condition that he returned to face the criminal charges against him.
Lawyer Georges Kapiamba said Mr Katumbi was taken to hospital in Lubumbashi, after police fired tear gas at him and his supporters.
The politician was weak but boarded the flight unaided, he added.
Mr Katumbi has condemned the charges against him as an attempt to stall his campaign to replace President Joseph Kabila in November polls.
Mr Kabila, in power since 2001, is nearing the end of his second term and he is constitutionally obliged to step down by December.
But there is growing political tension as it is not clear if he will relinquish power.
Who is Moise Katumbi?
Moise Katumbi was governor of the south-eastern Katanga province for almost a decade.
He is a wealthy businessman who has a lot of support in the mineral-rich south-eastern Katanga province, and was at one time an ally of the president,
But in September last year he broke ties with the ruling party when he accused President Kabila of wanting to cling to power.
His popularity is partly down to his job as the president of a great source of Congolese pride - football club TP Mazembe.
They are Africa's reigning football champions, having won the African Champions League for the fifth time in November.