The explosion came in the same week that 90 people were arrested in connection with skirmishes during campaigns, with the government insisting that any East African Community (EAC) election observers would have to undergo a 14-day mandatory quarantine on setting foot in the country.
The government said three people were killed during the first week of the campaigns in the attacks between the ruling party-affiliated group Imbonerakure and opposition party CNL supporters.
CNL party leader and opposition presidential candidate Agathon Rwasa said more than 200 of his supporters, including candidates who contested for legislative and local government, were arrested.
Mr Rwasa will be facing off with ruling CNND-FDD party presidential nominee Evariste Ndayishimiye, who is the chosen successor of President Pierre Nkurunziza, who has been in power for 15 years.
Police accused Mr Rwasa and his party members of incitement to violence during the campaigns.
