Henry Okah was arrested for allegedly masterminding the October 1 attacks in which 12 people died [Reuters]
Nigerian security forces have arrested the brother of Henry Okah, a former leader of the rebel Movement for the Emancipation of the Niger Delta (Mend), over his suspected involvement in deadly bombings in Abuja, the capital, on October 1.
Charles Okah was taken into custody at his home in the southern city of Lagos on Sunday.
He has been accused of helping to fund the twin car bombings that struck during independence anniversary celebrations in Abuja.
Henry Okah is alleged to have masterminded the attack that left 12 people dead and dozens of others injured.
Al Jazeera's Ama Boateng, reporting from the capital, confirmed that Okah had been arrested.
Boateng said: "We can confirm that Charles Okah, Henry Okah's brother, was arrested on Saturday afternoon in Lagos.
"This is in connection with the bombings in Abuja."
A government official said that Charles Okah was mentioned by suspects as a source of funds for the Abuja blasts.
"He is with us in Abuja," the official, who chose to remain anonymous, told reporters.
The arrest comes a day after a warning, signed Jomo Gbomo, the pseudonym used to claim the independence day blasts and years of attacks on oil and gas installations in the Niger Delta, was emailed to media saying that another bombing was planned for Abuja.
Security sources have said they believe several different authors have at times written the Jomo Gbomo emails, including both Henry and Charles Okah.
Henry Okah has said he did not have any involvement in the Abuja attacks.
"Apart from using the pseudonym Jomo Gbomo to threaten and cause confusion, he has been mentioned several times by suspects with us now as a source of funds for the blast," the security official said, referring to Charles Okah.
Rudi Krause, a lawyer for Henry Okah, denied that Charles Okah had ever written under the name Jomo Gbomo.
"I don't know the circumstances of his arrest but as far as we are concerned this is just part of the witch hunt against Mr Okah," Krause said.
"How can they suddenly claim that his brother is involved in this bomb attack? It is just absurd."
Henry Okah, who is believed to have led Mend in their battle to secure more of the country's oil wealth for the southern Niger delta region, was arrested in South Africa shortly after the October 1 attacks and faces terrorism charges.
Mend had issued a warning to journalists about an hour before the attacks, telling people to stay away from festivities at Eagle Square in Abuja.
One car bomb exploded, drawing police, firefighters and onlookers to the street near a federal courthouse. Five minutes later, a second car bomb exploded in the area.
Since the bombing, Mend has issued statements denying that Henry Okah, an alleged arms dealer who supplied weapons for the group's attacks on government and oil company targets, had any role in the attack.
At a court hearing on Friday in Johannesburg, a state prosecutor read a portion of Henry Okah's diary that suggested Charles had played a role in the Mend hierarchy.
"My brother Charles has faked my role and has been collecting money and negotiating a ceasefire claiming to be me," the diary reads, according to the prosecutor. "What treachery this is?"