Mr Ajaero and the NLC have been having running battles with the federal government over what the union described as a clampdown on the civic space by security agencies.
The Nigeria Labour Congress has announced the arrest of its President, Joe Ajaero, by security operatives.
The NLC, in a statement shared on its X handle, said Mr Ajaero was arrested by operatives of the State Security Service (SSS, also called DSS) "at the Nnamdi Azikiwe Airport Abuja this morning on his way to attend an Official engagement of TUC United Kingdom and he is now detained at the office of the NSA."
None of the security agencies has spoken about the arrest. The SSS recently redeployed its spokesperson, Peter Afunanya, without announcing a replacement.
Mr Ajaero and the NLC have been having running battles with the federal government over what the union described as a clampdown by security agencies.
Ajaero's travails
PREMIUM TIMES reported that the labour leader has been summoned twice by the police in recent weeks over allegations surrounding a Briton, Drew Povey, who owns a bookshop at the NLC headquarters.
The police, on 7 August, raided the bookshop located on the second floor of the Pascal Bafyau Labour House headquarters of the congress. Mr Povey was reportedly not in Nigeria at the time of the raid.
The Nigeria Police Intelligence Response Team (NPF-IRT) later summoned Mr Ajaero to appear for questioning over allegations of criminal conspiracy and terrorism financing.
Though Mr Ajaero was initially scheduled to appear on 20 August, he did not respond until 29 August because he was taking his master's degree examination.
The NLC President was again summoned alongside the union's General Secretary, Emmanuel Ugboaja, by the Police through the Nigerian Police Force Intelligence Department (NPF-FID). Although they were to appear on 5 September, their legal team requested they be allowed to do so on 24 September.
The Nigerian government claims that Mr Povey was spearheading a plot to overthrow President Bola Tinubu.
The police issued a warrant of arrest against him while the Federal High Court formally declared him wanted. The court also issued arrest warrants for two Nigerians allegedly linked to the Briton.
Mr Povey has, however, denied the allegation and urged the government not to criminalise peaceful protests in Nigeria.
Sign up for free AllAfrica Newsletters
Get the latest in African news delivered straight to your inbox
Calls for unconditional release
Meanwhile, the NLC and Amnesty International have demanded the immediate and unconditional release of Mr Ajaero by security agencies.
The NLC, in a statement by its spokesperson, Benson Upah, said it "will not stand idly by while the rights of its leaders and members are trampled upon."
In its statement, Amnesty International said it "strongly condemns the unlawful arrest of the President of Nigeria Labour Congress (NLC) Joe Ajaero by the Department of State Services (DSS) today. The labour union leader must be immediately and unconditionally released."
"The arbitrary arrest of Joe Ajaero shows an escalating crackdown on human rights and restrictions on civic space by the government of President Bola Tinubu."
"President Bola Tinubu's government persistently attacks and undermines the operations of the NLC, through fabricated allegations, raids on NLC headquarters and other forms of harassment and intimidation. This growing culture of impunity and disdain for workers' rights to organize and seek better welfare must stop.
"President Tinubu is setting a new record of utter disregard for the rule of law," Isa Sanusi, head of Amnesty International in Nigeria, wrote in a statement.
