ABUJA (Reuters) - Nigeria’s security forces stopped lawmakers entering parliament on Tuesday in a blockade seen by the opposition as a bid to intimidate its leaders, but the presidency condemned the move and the acting president fired the head of the security agency.

It is the first such incident since Nigeria became a democracy in 1999 and coincides with increased tension between the National Assembly and the executive ahead of an election in February 2019 when President Muhammadu Buhari will seek a second term.

For some, it revived memories of the decades when the military and security forces held sway over politics in a country that has one of Africa’s largest economies.

Armed men wearing the black uniform of the Department of State Security (DSS) stood at the gates of the building in the capital Abuja and were later joined by police officers blocking entry for up to an hour, witnesses said.

Images of the incident were shared widely on social media. The motive for the blockade was not immediately clear.

But a spokesman for Vice President Yemi Osinbajo said in a statement that the DSS director general, Lawal Musa Daura, had been fired. Osinbajo is acting president for Buhari, who last week left for a 10-day holiday in Britain.

“The unlawful act, which was done without the knowledge of the presidency, is condemnable and completely unacceptable,” said a separate statement issued later by Osinbajo’s office.

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It described the move as an “unauthorized takeover of the National Assembly complex” which was “a gross violation of constitutional order, rule of law and all accepted notions of law and order”.

The statement gave no reason for Daura’s dismissal. The presidency later said Matthew B. Seiyefa, the most senior director in the DSS, will act as director general until further notice.

DEFECTION

The blockade followed the defection of around 50 lawmakers from Buhari’s ruling All Progressives Congress (APC) party to the main opposition in the last few weeks. These included the country’s third most senior elected official, Senate President Bukola Saraki.

The defections cost the APC its Senate majority and present a challenge to Buhari’s re-election bid because most of those who left joined the opposition People’s Democratic Party which ruled Nigeria from 1999 until Buhari took office in May 2015.

Saraki’s supporters said the blockade was part of a plan to impeach and replace him. Parliament went on recess last week until Sept. 25 but meetings were to be held on Tuesday.

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“We urge Nigerians and the international community to condemn this illegal invasion of the National Assembly complex and the attempt to asphyxiate the legislature as undemocratic, uncivilized and irresponsible,” said Saraki in a tweet.

After the blockade, Saraki’s supporters greeted him with chanting in the parliament building.

“The presidency’s sack of Daura was a damage-control stunt and a knee-jerk gimmick which came as a response to the national and international outcry against the armed invasion of our legislature,” said a PDP statement.

The ruling party said attempts to blame its leaders for Tuesday’s blockade were “false allegations” and “mischievous”.

“The use of armed security agents to force political outcomes does not bode well for the February 2019 general election,” said Malte Liewerscheidt, vice president at Teneo Intelligence, in a note.