Rwandan police have arrested three people in connection with a grenade explosion in the capital Kigali.
They are investigating if the blast may be connected to other explosions in the same area earlier this year.
Witnesses have told the BBC how they ran to the wounded to give first aid after the grenade exploded in a busy street.
The blast in Kigali came just two days after President Paul Kagame was re-elected in a landslide win.
His re-election came amid criticism that opposition voices have been unfairly suppressed.
A team of Commonwealth observers in Rwanda said there had been no real competition in the election, after some candidates were barred from standing.
US Journalist Steve Terril was in the street where the grenade went off.
"I saw several people on the ground injured," he told the BBC's Network Africa.
"One was bleeding so we went down to assist some people who were traumatised."
He said the explosion was not very large and that he did not see anyone running away from the scene.
Police have not released any details about the suspects.
The investigation was continuing and there could be further arrests, a police spokesman said.
There were several grenade attacks in Kigali earlier this year amid rising political tension ahead of this month's presidential election.
The government put the blame for those attacks on two former high-profile figures in the ruling RPF party who have gone into exile in South Africa.
They have denied the accusations and say they fled because President Kagame does not tolerate dissenting views.