Four Salvadoran soldiers serving with Haiti's UN-backed Gang Suppression Force were missing on Monday, October 19, after gangs ambushed their armored vehicle in the Santo area of Croix-des-Bouquets, just east of Port-au-Prince, on Sunday.

It is the first major attack on the force since it began operations, the Associated Press reported.

El Salvador's armed forces said the four aviation technicians were returning to camp when attackers hit the vehicle with gunfire and explosives and set it on fire. “Four soldiers managed to get out of the vehicle,” the military said. Helicopters sent to help came under fire, and “multiple attempts to approach by land and air have been made, but these have been hampered by the intensity of the fighting.”

The force said its personnel returned fire under its rules of engagement, with helicopter support, and urged residents of Santo to stay indoors. As of Monday, neither the force, the Salvadoran military nor the Haitian police had confirmed the soldiers' whereabouts or condition. Reports on social media that they had been captured or killed were unverified.

No group has claimed responsibility. The area is controlled by the Kraze Baryè gang of Vitelhomme Innocent and the 400 Mawozo gang, whose leaders are under UN and U.S. sanctions. “Others want to show that they can strike back,” said Romain Le Cour of the Global Initiative Against Transnational Organized Crime. If the soldiers are being held, he said, the gangs gain leverage.

The force has more than 1,500 troops in Haiti, from countries including El Salvador, Chad, Jamaica and Guatemala, and is awaiting more contingents from Sri Lanka and Guatemala. The UN Security Council was scheduled to discuss Haiti on Monday.