Nigeria’s acting President Yemi Osinbajo has appointed a new boss for the domestic spy agency after masked gunmen took control of the parliamentary building on Wednesday, causing a political uproar in the West African state.

Matthew Seiyefa would act as the new director-general of the Department of State Security Service (DSS), replacing Lawal Daura who was sacked for what Mr Osinbajo's office called the "unlawful takeover" of the parliamentary complex.

It is unclear why the masked gunmen — linked to the spy agency — took control of the building, but opposition lawmakers said it was an attempt to intimidate and block them from entering parliament after they defected from the ruling party.

The presidency denied authorising the move, which comes amid a surge of tension between President Muhammadu Buhari and political rivals.

The DSS has often been accused of high-handedness and abuses against perceived political opponents of the Buhari administration.

Parliament began a two-month recess on July 24.

Senate battle

Independent sources speculated that Tuesday's action was a show of strength connected to a political crisis ahead of presidential and parliamentary elections next February.

Lawmakers loyal to Buhari's All Progressives Congress (APC) are believed to be planning to oust the president of the Senate, Bukola Saraki.

Saraki, the country's third-highest ranking politician, last week dumped the APC for the main opposition Peoples Democratic Party (PDP).

The APC has called on him to resign, suspecting him to be the force behind defections that have damaged the party's standing and Buhari's chances of re-election.

On the last day before recess, 14 members of the 109-seat senate and 37 members of the 360-seat House of Representatives left the APC.

Party primaries are due between this month and October, coinciding with mounting discontent at Buhari's style of government and handling of widespread violence across the country.