GATUMBA, Burundi - Two people were killed when a bus carrying 30 passengers was ambushed by armed men believed to be ex-rebels near Burundi&39;s capital Bujumbura, officials said on Sunday.

The bus was attacked on Saturday near Gatumba on the outskirts of Bujumbura and close to the border with the Democratic Republic of Congo, a local government official, Jean-Marie Mutabazi, told journalists.

"The bandits fired on the vehicle. One person was killed immediately and another died later in hospital," he said, adding that at least a further 10 people sustained serious injuries.

A survivor interviewed on the radio said the attackers were members of the National Liberation Forces (FNL), a former rebel group.

"We were attacked by about 15 FNL, wearing military uniforms and heavily armed," he said, adding that the attackers sang FNL songs and tore up a ruling party flag during the attack.

That account was confirmed to reporters by a senior police officer who asked not to be named.

"It&39;s a group of residual FNL that crossed over from the Democratic Republic of Congo to launch the attack and then crossed back again," he said, adding that it was the first attack of its kind since 2011.

Burundi has seen a resurgence of violence since the disputed 2010 elections, but the authorities have dismissed rebels who have taken up arms again as "armed bandits".