The workers are on a four-day warning strike, which began on Monday, to press home their demands for payment of their outstanding salary arrears and better condition of service, among others.
A News Agency of Nigeria (NAN) correspondent at the scene reports that the main entrance from the Federal Secretariat was barricaded by the operatives, majority of whom were police operatives.
Motorists and PASAN members were denied entry by the security operatives, who said they were acting on instruction.
But non-members, including lawmakers, their aides, journalists, bank officials, vendors and others, were allowed in.
NAN reports that the National Assembly leadership had on Monday directed “the Police and the State Security Service (SSS) to ensure adequate security within the vicinity of the National Assembly from Tuesday”.
The directive was announced by the Clerk, Sanni Omolori, through a statement.
“This is to enable members of staff to come in and perform their legitimate duties without any hindrance.
“The directive was passed after a meeting of the joint leadership of the two chambers with the management and representatives of the security agencies,” Omolori said.
Addressing newsmen at the gate on Tuesday, the Chairman of PASAN, NASS chapter, Mr Musa Muhammad, described the shutdown as unfortunate.
He said the action was a demonstration of the insensitivity of authorities to the plight of the workers.
Muhammad said, “The management of the National Assembly has helped us by barricading the gate, and not allowing the staff to enter.
“I think they have shot themselves in the foot. This is to show the world that they are insensitive to the plight of the staff. The staff are law-abiding citizens.
“We have never carried out this kind of action before, and to make the whole case worse, you cannot ask your staff to stay outside.”
He denied allegation that the association prevented non-members from entering the complex to carry out their lawful duties.
Muhammad also said PASAN was not behind the disruption of electricity and water supply in the complex on Monday.
“We never asked anybody not to go and perform their duties. Ours is for own staff.
“Yesterday, bankers were allowed in, all other workers who are not our members were allowed in.
“Not even the legislators, we have never stopped them from carrying out their legitimate function.
“We didn’t instruct anybody to shut down electricity and water supply, and as I speak with you we are not sure that was carried out by our members,” he added.
The PASAN chairman said the strike was not planned to disrupt the planned presentation of the 2019 Appropriation Bill by President Muhammadu Buhari to the National Assembly on Wednesday.
Meanwhile, water and electricity supply has been restored in the complex, NAN reports.