The suspect was arrested in the early hours of yesterday morning and taken to a Johannesburg police station for questioning.
Sources close to the investigation said the arrested man is a former member of the Rwandan army and worked under Nyamwasa for a number of years.
Nyamwasa was shot in the stomach in the driveway of his home when he returned from a shopping trip with his wife, Rosette, on Saturday morning.
He is in a stable condition at the Morningside Clinic, in northern Johannesburg.
Rosette has blamed Rwandan president Paul Kagame for the shooting. Kagame and Nyamwasa were close associates until a dispute early this year.
The police could not confirm yesterday that the man in custody had links to the Rwandan government.
Insiders say the suspect has had a long working relationship with Nyamwasa.
« The families of the alleged shooter and of Nyamwasa lived together in exile, » said one.
The man in police custody is still being questioned.
« He must be released after 48 hours, according to the Constitution, if he is not linked to the crime, » the police said.
Police are still searching for a second suspect in the shooting.
Gauteng police spokesman Brig Govindsamy Mariemuthoo refused to confirm the arrest.
« I cannot confirm or deny the arrest. We are still investigating the motive and if there is an arrest it would form part of the investigations, » said Mariemuthoo.
The Times has established that Nyamwasa was being driven in a black BMWX3 with his wife from the Blue Bird shopping centre when a man, on foot, followed their car into their Athol Mews complex.
The man, who was wearing a red T-shirt, struck the driver’s side window, screaming « Stop, stop, stop ».
Security personnel at the complex tried to prevent the man from entering the complex but he ignored them.
The driver opened the window half way but continued driving.
« The man clung onto the window while the car was moving. He then pulled out a firearm, cocked it and fired a single shot at Nyamwasa, » said an insider.
The man, who is believed to have been in the company of an accomplice, was seen fleeing on foot.
Security guards at the complex are believed to have run for cover during the shooting.
Nyamwasa was rushed to a hospital. His two children, who are in South Africa on holiday, were in the house when their father was attacked.
Police found one round of live ammunition as well as a cartridge case at the scene.
An attempted murder docket has been opened.
The police have asked for surveillance camera film from the shopping centre to establish whether the couple were followed.
Fingerprints were taken from Nyamwasa’s car and police are expecting results soon.
Police sources appear to agree with Nyamwasa’s wife that the shooting was politically motivated.
« How can you conclude that this was a robbery when nothing was taken? » said one officer.
Rosette Nyamwasa was quoted as saying that she believed the shooter had, after firing the first shot, gone to the passenger side of the car, from where he attempted to fire a second shot – but the gun jammed.
Nyamwasa, an outspoken critic of President Paul Kagame, fled from Kigali with his family in February. The couple were assigned a security guard but he was nowhere to be seen at the time of the attack.
« I think it was our government, » Rosette reportedly said.
Her husband had accused Kagame of corruption and claimed that the judiciary was compromised. Arrest warrants for Nyamwasa were reportedly issued for his alleged role in theRwandan genocide. – Additional reporting by Judy Lelliott