Burundi's main opposition party has accused the government of planning simultaneous grenade attacks against its leaders at the weekend.
Burundi is only now emerging from a bitter civil war
Frodebu said the vice chairman and others were assassination targets.
Unidentified gunmen on Sunday threw hand grenades at the homes of five politicians opposed to the president, wounding three people.
Divisions within the ruling CNDD-FDD party have prompted fears of renewed following a decade of civil war.
"I heard two explosions while I was sitting inside the house with visitors. Fortunately, no-one died, just my car and windows of my house were damaged," Nephtalie Ndikumana, an opposition member of parliament told Reuters news agency.
Police in Burundi say they are investigating the attacks.
The targeted leaders were among 69 MPs who signed an open letter to President Pierre Nkurunzinza asking him to resume talks with the opposition.
Since a new cabinet was appointed last month, members of parliament from opposition parties have refused to pass bills presented by a government they refuse to recognise.
In a statement issued in Bujumbura, Frodebu accused President Nkurunzinza of pushing the country into a fresh cycle of violence.
"The Frodebu party strongly condemns these assassination attempts organised and planned by the government and the ruling party," the statement said.
The ruling CNDD-FDD party lost their majority in the National Assembly after the party ousted its formerly influential chairman Hussein Radjabu - accusing him of trying to destabilise the country.
Mr Radjabu is in jail awaiting trial and a group of 17 legislators still allied to him and have formed a coalition with opposition MPs to frustrate the government in parliament.