The Nigerian Bar Association (NBA) has decided to embark on a two-day warning boycott of all courts in Nigeria over the suspension of the country's top judge Walter Onnoghen.

The association made the decision at its emergency national executive committee (NEC) meeting in the Nigerian capital, Abuja, on Monday, The Cable news in Nigeria reported.

Nigeria's President Muhammadu Buhari suspended Onnoghen on Friday and replaced him with acting chief justice Ibrahim Tanko Muhammed weeks before an election in which the judiciary could play an important role.

The chief justice was due to face trial on charges of allegedly failing to declare his assets, which Onnoghen has argued is without merit. But it was adjourned indefinitely on Monday, the chairman of the Code of Conduct Tribunal (CCT) said.

On Friday, the main opposition candidate, Atiku Abubakar, called the president's decision "an act of dictatorship".

The NBA and local civil society associations held protests in Abuja and southeast Enugu state to reject Onnoghen's suspension, calling it an "attempted coup against the Nigerian judiciary".

Onnoghen has helped resolve electoral disputes in past elections, some of which have been marred by violence and vote-rigging. The chief justice could preside over a disputed election result.

The Members of the @NigBarAssoc have kicked off their Rally today, at the NBA Headquarters, Abuja, against the suspended Chief Justice of Nigeria Hon. Justice S.W.N Onnoghen by Mr President @MBuhari @Abuja_Facts @lawalhab @Nigerialawyers @LegalNaija pic.twitter.com/LcFPzkbKKA — Call To Bar Naija (@CallToBarNG) January 28, 2019

Buhari 'has done no wrong'

Critics say the suspension is an effort by Buhari to weaken Nigeria's judiciary and pave the way for his election to a second term in the February 16 vote.

Amid growing criticism, Nigeria's information minister denied the suspension was related to the elections.

Minister Mohammed Alhaji Lai said it had "nothing to do with the forthcoming elections" and did not "signify the onset of dictatorship or tyranny as some have insinuated".

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The chief justice plays a key role in any legal challenge to what could be a disputed vote.

The United States, Britain and the European Union said Buhari acted "without the support of the legislative branch". The US warned this suspension could "cast a pall" over the election.

On Monday, the presidential spokesman, Garba Shehu, said Buhari broke no laws in the suspension and "has done no wrong".

With tensions before the vote, observers warned against election-related violence.

Oil-rich Nigeria struggles against multiple security challenges, including the decade-old Boko Haram rebellion, and Buhari's 2015 election was a rare peaceful transfer of power. Diplomats have urged the top candidates to sign a peace pledge.