An official says at least six people have been killed in a gun attack believed to have been orchestrated by rebels opposed to President Pierre Nkurunziza.

Aloys Ngenzirabona, the mayor of Gisuru in Ruyigi province, where the attack happened Monday night, told The Associated Press of the deaths and said many others were injured in the attack.

Gisuru resident Abdul Komezamahoro said seven gunmen ran through a market, firing randomly before fleeing.

The attackers are believed to be connected to a group of exiles in Tanzania led by Leonidas Hatungimana, a former presidential spokesman who was sacked last year after he advised Nkurunziza not to seek a third term. Nkurunziza's controversial third term, which he won in July, set off rounds of political violence killing more than 400 people.