PORT-AU-PRINCE, April 12 (Reuters) - Haiti declared three days of national mourning on Sunday, a day after a deadly stampede killed 25 people during an annual celebration thronged by students and visitors at its Laferriere Citadel tourist attraction.

In a national address, Prime Minister Alix Didier Fils-Aimé said mourning would begin from Tuesday, and the government would cover the funeral expenses for disaster victims.

Earlier in the day, Emmanuel Pierre, the national head of the civil protection authority, told Reuters authorities had revised down the death toll to 25 from an initial tally of 30.

The early-19th-century fortress built shortly after Haiti's independence from France is a UNESCO World Heritage site.