Witnesses said several vehicles were damaged by a bomb that rocked central Kigali, leaving scores injured and at least six people dead.
Reporters for the Rwanda News Agency said as many as 12 people were listed in critical condition at a nearby hospital. Authorities told the news agency three people were in custody for the bombing.
Business had returned to normal by Thursday near the blast area, though the security presence was high.
The explosion followed the Wednesday announcement by the Rwanda National Election Commission that Paul Kagame won his bid for a second term in office with 93 percent of the vote.
More than 5 million Rwandans cast ballots Monday in the second presidential election since the 1994 Rwandan genocide campaign against the Tutsi ethnic community.
Kagame gained popularity when as a guerrilla leader he helped restore security to a country plagued by a devastating genocide campaign in 1994.
Kagame faced criticism from opponents who said he systematically wiped out many political rivals. South Africa last week recalled its ambassador to Rwanda over an assassination attempt on an outspoken critic to the Rwanda president.
Kagame deflected the criticism Monday, saying the international community was looking at his country through the lens of the genocide campaign.