Burundi’s former President Domitien Ndayizeye is challenging a decision by the electoral commission to ban him from running in May’s presidential election.
The 61-year-old says he submitted his papers with 208 nominations, eight more than required.
“I was shocked to hear it – I could get 10,000 [nominations] in a matter of hours,” Mr Ndayizeye told BBC Great Lakes.
Mr Ndayizeye served as president from 2003 to 2005 – a critical time when peace agreements were signed to end more than a decade of civil war.
The electoral commission also rejected three other candidates, allowing six to run in the elections in May.
BBC World Service Africa editor Will Ross says there is growing concern about the lack of democratic and political space in Burundi.
Mr Ndayizeye’s complaint that he has been unfairly prevented from standing is not the only sign that May’s vote is likely to be controversial, he says.
This week a UN commission of inquiry this week warned about the deteriorating human rights situation in Burundi.
It said a youth league linked to the governing party continued to kill, torture and harass the opposition.
The government has dismissed similar allegations before.
Whoever wins the election may find that they are not entirely in charge.
Even though the current president is to step down, Pierre Nkurunziza may retain considerable power because under a controversial new law he is due to be given the title of “supreme leader”.