A total of 22 persons were killed on the spot and nine died later from their injuries in a attack staged by unknown gunmen on Sunday night which targeted a bar at Gatumba in the province of Bujumbura Rural, some 15 km west of the Burundian capital Bujumbura, an administration official told Xinhua on Monday. The attack also injured several others. \"The attack occurred at about 20H00 (18H00 GMT) at \"Les Amis\" Bar when gunmen in military and police uniform blasted grenades and opened fire at a crowd of people who were taking drinks,\" head of Gatumba zone Emmanuel Masumbuko told Xinhua. He said \"22 persons were killed immediately while an unknown number of others were injured, many of them seriously.\" The head of Gatumba zone said the slightly injured persons were taken to clinics at Gatumba while those who had been seriously injured were evacuated to hospitals in the capital Bujumbura. Masumbuko said \"six of the seriously injured persons who had been admitted to Prince Régent Charles Hospital in Bujumbura have already died and three others who had been admitted to Roi Khaled University Hospital have also succumbed.\" According to the head of Gatumba zone, the attackers have not yet been identified and did not steal anything from the bar. The locality of Gatumba is a stronghold of the Forces Nationales de Libération (FNL) rebel movement, formerly known as Parti pour la Libération du Peuple Hutu-Forces Nationales de Libé ration (PALIPEHUTU-FNL), which was led by Agathon Rwasa. FNL has together with some opposition parties pulled out of the east African nation\'s electoral process in June 2010, denouncing massive fraud in the May 24 communal elections, the first in a series of five polls. After boycotting the electoral process, Agathon Rwasa and some other opposition leaders went into hiding for fearing for their security. Analysts say it is a rebel movement in creation, but the Burundian government calls those attackers \"simple bandits.\"