Bujumbura (Burundi) (AFP) - Gunmen in Burundi dressed in military fatigues executed three ruling party activists in a bar, police said Tuesday, the latest attacks to spark alarm months ahead of elections.

The attack -- which saw gunmen burst into the bar, push the men to the ground and shoot them, after which they torched the local party office -- follows heavy clashes between the army and rebels last week in which some 100 insurgents were reportedly killed.

The army has said the rebels had planned a major offensive to destabilise the country ahead of elections due in May and June.

Burundi, a small nation in Africa's Great Lakes region, emerged in 2006 from a brutal 13-year civil war and its political climate remains fractious ahead of the polls.

"They tied them up on the ground, then killed them with automatic weapons," said a local official, speaking on condition of anonymity.

Police confirmed the attack, which took place late Sunday in the eastern Gisuru region, some 250 kilometres (155 miles) east of the capital Bujumbura.

The five gunmen -- who police spokesman Pierre Nkurikiye called "bandits" -- then left without stealing anything to set fire to a nearby office of the ruling CNDD-FDD party.

President Pierre Nkurunziza, in power since 2005, is expected to run for a third term in office despite opponents' claims that this would violate Burundi's constitution.

Onesime Nduwimana, spokesman of Nkurunziza's CNDD-FDD party, condemned the "political" attack on the bar.

"It is very serious, because it is a crime that is certainly political in nature," Nduwimana told AFP.

"We believe those who committed this cowardly crime belong to the extremist fringe of the Burundian opposition, with the aim of sabotaging the 2015 elections."





- 'Alarming' -





While the identity of the gunmen is not known, Nduwimana said he feared they wanted to destabilise the country by "sowing hatred" and provoking revenge attacks by the Imbonerakure, a controversial youth wing of the CNDD-FDD.

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"We ask that those responsible for these crimes are prosecuted wherever they are," Nduwimana said.

The violence has raised fears of wider trouble.

"What is happening today in Burundi is extremely worrying," said Charles Nditije, one of the main leaders of the opposition, pointing to the heavy fighting between gunmen and the army in the western Cibitoke region last week.

Burundian officials and witnesses said the group of unidentified rebels crossed into Burundi from Democratic Republic of Congo's eastern Kivu region, a chronically unstable and resource-rich area that is home to dozens of rebel groups.

"The international community is very concerned about these developments, a few months before the start of a crucial electoral process in Burundi," said a diplomat, speaking on condition of anonymity.

"How far will this go? We do not know, but it has become alarming."

The violence adds to an already volatile political climate, with the opposition reporting arrests, harassment, and a clampdown on free speech.

Nditije, like other opposition members, denounced what he claimed was "massive fraud" in the election preparation process, including voter registration.

"If nothing is done this can lead to a major crisis," he said.