President of the Nigeria Labour Congress (NLC) Joe Ajaero has said he was grilled for about 15 hours over the #EndBadGovernance nationwide protests that took place in August.
Mr Ajaero was arrested around 7 am on Monday by the Department of State Services (DSS) at the Nnamdi Azikiwe International Airport, Abuja.
The labour leader was on his way to the United Kingdom for a Trade Union Congress (TUC) event when he was arrested.
He was released on bail around 11 pm.
The NLC leader told Channels TV that his travel passport was seized by the secret police.
According to him, some police officers came to the DSS facility to grill him.
Ajaero said he was questioned over alleged terrorism financing involving a British national Andrew Wynne who is wanted by Nigerian authorities.
The TUC, global rights group Amnesty International, as well as human rights activist Femi Falana, among others, berated the Federal Government for clamping down on the labour leader and demanded his immediate and unconditional release.
Ajaero met the police in late August to face questions over allegations of terrorism financing. He was scheduled to meet the police again before his arrest.