Nigerian intelligence agency spokeswoman Marilyn Ogar told the BBC it's likely Henry Okah would be formally charged Monday for having a role in Friday's bombings near security offices as the country celebrated 50 years of independence from Britain.
The blasts killed 12 people.
Okah was one of the founders of the Movement for the Emancipation of the Niger Delta, or MEND, which staged attacks and took hostages to disrupt oil operations. The group claims native Nigerians aren't seeing enough benefits from the oil revenues.
Some 50 Interpol agents raided Okah's Johannesburg home Friday night after the explosions at the request of the Nigerian government, but no weapons were found, reports said.
Okah told the BBC he had nothing to do with the attacks.
Nigerian President Goodluck Jonathan denounced MEND as nothing more than terrorists pretending to be fighting for a cause, the report said.