Haiti's supreme voodoo leader has vowed to wage "war" after Evangelicals attacked a ceremony organised by his religion honouring those killed in last month's massive earthquake.

The attack on Tuesday in the capital's sprawling Cite Soleil slum came amid rising religious tensions, as Protestant Evangelicals and other denominations recruit followers in the wake of the earthquake that killed more than 200,000.

Some of the fresh converts have said they did so because they believed God caused the earthquake.

"It will be war - open war," Max Beauvoir, supreme head of Haitian voodoo, said in an interview at his home and temple outside the capital.

"It's unfortunate that at this moment where everybody's suffering, that they have to go into war. But if that is what they need, I think that is what they'll get."