BUJUMBURA, June 11 (Xinhua) -- An unidentified person Sunday night blasted a grenade in a crowd in front of a shop at Birohe village in Gitega province, central Burundi, killing one person and injuring 21 others, the governor of Gitega said Monday.

The attacker took advantage of obscurity as it was the night fall at about 7:10 p.m. local time when he blasted the grenade, said Venant Manirambona in a telephone interview with Xinhua.

"A woman selling small objects and aged about 60 years was killed on the spot. 21 persons were injured and six of them were seriously injured and evacuated to hospital," said Manirambona.

The attacker might have been targeting one person who was in the crowd, said the governor, who described the explosion as "terrorism."

He also denied any link with political motivations behind the explosion.

Burundian President Pierre Nkurunziza last Thursday signed and promulgated the new constitution in the province. After that he announced that he will leave the presidency in 2020 at the expiry of his current presidential term.

Burundi's new constitution extends the presidential term from five to seven years and allows the president to serve two consecutive terms, which means Nkurunziza is allowed to stay in office until 2034 if he is elected in future presidential elections.

Burundi plunged into a crisis in April 2015 when Nkurunziza decided to run his controversial bid for a third term. His candidature, which was opposed by the opposition, resulted in a wave of protests, violence and even a failed coup in May 2015.