Mask-wearing officers of the State Security Services have thrown a cordon over the National Assembly, in what some lawmakers say is aimed at aiding the removal from office of the Senate president, Bukola Saraki.
Deputy senate president Ike Ekweremadu, is also being targeted, PREMIUM TIMES understands.
The leader of the SSS team at the National Assembly entrance, said the siege was "an order from above".
"We need more guns, send us more guns," the officer, who wore no name tag, was heard shouting openly as National Assembly staff and journalists at the gate watched.
As early as 7 a.m. Tuesday morning, the main entrance of the building was blocked by the security operatives.
Staff of the assembly have been denied entrance into the premises by security personnel in black and blue uniforms.
PREMIUM TIMES also observed one of the senators, Rafiu Ibrahim, making frantic calls while standing at the entrance.
It is unclear whether he was denied access or not.
Mr Ibrahim is a pro-Saraki senator from Kwara state.
It is also not immediately clear whether some senators had already entered the chamber.
A police officer who spoke with PREMIUM TIMES, denied knowledge of the situation.
"I don't know what is happening. I'm seeing it just like you and I'm surprised, " he said.
As at the time of filing this report, more policemen are arriving the National Assembly.
Some lawmakers had in past few days insisted Mr Saraki, stepped down from his position having defected from the majority party.