Nigerian lawmakers were temporarily blocked from entering parliament in Abuja by armed men, some of whom were masked, reports Reuters news agency.
Witnesses told Reuters that the security agents, wearing the black uniform of the Department of State Security, allowed lawmakers to enter an hour or so later, but continued to bar government agents and journalists.
Video tweeted from the scene by an aide to Senate President Bukola Saraki shows a politician confronting the masked gunmen:
Nigeria’s Acting President Yemi Osinbajo – in post while President Buhari is on holiday – has said he will investigate the blockade.
An emergency leadership meeting had been called at the National Assembly for midday (11:00 GMT), the BBC’s Chris Ewokor reports.
Political tension has increased following the defection of some members from the ruling party to the opposition, including the Senate President Bukola Saraki, whose role makes him Nigeria’s third-most senior politician.
There are indications that parliament is planning to reconvene to consider the election budget requested by President Buhari, our reporter says.
The presidency says that a delay in approving the budget and other requests could adversely affect next year’s presidential and legislative polls and even lead to a government shutdown.