DSS operatives blocked entrance to the National Assembly on Tuesday morning.
The blockade comes ahead of a reported emergency meeting between Senate President Bukola Saraki and NASS leadership.
It also comes barely a day after Senate Leader Ahmed Lawan met Vice President Osinbajo in Aso Rock. Reports say pro-APC lawmakers want to impeach Saraki and elect Lawan in his place. There are also plots to remove Deputy Senate President Ike Ekweremadu, reports say.
Critics say the DSS blockade is an attack on democracy.
WATCH: Senator Ben Murray-Bruce vows to report APC leadership to international community over NASS blockade
Peoples Democratic Party (PDP) had accused President Muhammadu Buhari of going on vacation to London to allow the ruling All Progressives Congress (APC) collude with security agencies to subvert Nigerian democracy.
But APC denied the claims.
Critics say the ongoing National Assembly blockade is proof APC lied.