Burundi has sentenced a top opposition chief to five years in prison for bribery and arrested another for having links to a rebel group, according to opposition leaders.
Action against the two leaders in the central African country came amid growing fears of the risk of violence ahead of elections, with a string of attacks including a five-day battle earlier this month between the army and rebels.
The two leaders were the latest of several politicians to face criminal charges ahead of the polls in May and June.
Opposition leaders said the arrests were the government's way to block them from running for seats.
Frederic Bamvuginyumvira, a former Burundian vice-president and current deputy leader of the Front for Democracy (Frodebu) party, was sentenced on Thursday to five years in jail for bribery following a sex scandal.
He told the AFP news agency that the sentence by the country's anti-corruption court was made to "remove me from the electoral race".
Youth leader arrested
Frodebu youth leader Patrick Nkurunziza was also arrested on the same day. He is the most prominent figure held in connection with a rebel force that entered the country from neighbouring eastern Democratic Republic of Congo earlier this month.
The army, who said they killed around 100 of the rebels, said documents they seized showed the fighters had planned a major offensive to destabilise the country.
Burundi, a small nation in central Africa's Great Lakes region, emerged in 2006 from a brutal 13-year civil war and its political climate remains fractious ahead of the polls.
President Pierre Nkurunziza, in power since 2005, is expected to run for a third term in office despite opponents' claims that a new mandate would violate Burundi's constitution.
Burundi's last elections in 2010 were boycotted by most opposition parties, and opponents are again accusing the ruling CNDD-FDD party of eliminating dissent.
Bamvuginyumvira, a highly respected leader with a reputation for being tough on corruption, was Burundi's vice president from 1998 to 2001.