UPDATE 2-Gunmen kill at least 36 in Burundi bar attack
* Some gunmen dressed as policemen
* Attack heightens fears of a growing rebellion
* Growing number of former rebels returning to bush
* Former FNL boss moving between DR Congo and Burundi (Adds witness, colour from scene, analyst)
By Patrick Nduwimana
Bujumbura, Sept 19 (Reuters) - Gunmen have stormed a bar in Burundi killing at least 36 people, the deadliest attack in the Central African country this year that has heightened fears of a return to civil war.
Witnesses said the gunmen, some disguised as policemen, burst into the bar late on Sunday, forced its patrons to the ground and raked the interior with bullets.
Burundi has enjoyed relative peace since the former Hutu hardline rebel Forces for National Liberation (FNL) laid down their weapons and joined the government in 2009 after two decades of insurgency.
But attacks against civilians and soldiers have intensified since elections last year were widely boycotted by the opposition. Tit-for-tat fighting between the security forces and former militia fighters risks blowing up into a full-scale rebellion, analysts said. Continued...