PORT-AU-PRINCE (Reuters) — Shots and tear gas were fired Sunday near the presidential palace in Haiti’s capital, Port-au-Prince, during a protest organized by police officers demanding better pay and working conditions.

Officers told The Associated Press that at least three police officers were wounded.

It was not immediately clear who fired the shots or the tear gas during the protest, which coincided with the start of Carnival celebrations. A stage built by the Ministry of Defense and guarded by the army was also set on fire, a witness told Reuters.

The protest was one of several that police officers have organized since the end of last year as the perennially poor country struggles with a prolonged economic and political crisis.

Some protesters wore cream and blue police uniforms and carried guns, but had their faces covered, as they marched from the upscale Delmas neighborhood toward the large Champ de Mars public square, the main site for Carnival.