Officials say the plotters had attempted to take over the state media building but "they failed".
Authorities have instituted fines for breach of Covid measures as they say residents have not been following rules.
Kenya had expected to extend a debt repayment moratorium from bilateral lenders but some lenders were uncomfortable.
Prime Minister's Prosperity Party secured a new five-year term in the first round in June.
At least two grenades exploded in a bus parking lot in Bujumbura's city centre.