Another peacekeeper was seriously injured in the explosion and remains in hospital.
UNIFIL was unaware of the origin of the projectile and has launched an investigation to determine the circumstances.
“No one should ever lose their life serving the cause of peace.”said the mission.
Ensure the safety of UN personnel
The Secretary-General strongly condemned the incident, which occurred in the context of the escalating conflict in the Middle East.
“This is one of a series of incidents that have endangered the safety of peacekeepers, including in the last 48 hours,” UN spokesman Stéphane Dujarric said in a statement.
“Once again, the Secretary-General calls on all actors to comply with their obligations under international law and ensure the security of UN personnel and property at all times.”
Possible war crimes
The UN chief recalled that attacks on peacekeepers are serious violations of international humanitarian law and UN Security Council Resolution 1701 (2006) and may constitute war crimes.
UNIFIL supports the implementation of the resolution, which ended hostilities between Israeli forces and Hezbollah that broke out almost two decades ago. Read more in our explainer.
“There will need to be accountability”the statement said.
De-escalation resource
The Secretary-General expressed his deepest condolences to the family, friends and colleagues of the deceased peacekeepers, and to the country of Indonesia. He wished the injured officer a speedy and complete recovery.
Guterres also expressed his deepest gratitude to the men and women serving in UNIFIL, underscoring the importance of their security and freedom of movement.
The UN urged the parties to immediately de-escalate tensions and fully comply with their obligations under the Security Council resolution.
More than 50 health workers killed this month
Meanwhile, the World Health Organization (WHO) reported the loss of another medical professional amid the escalation.
“Israel’s expansion of military operations in southern Lebanon has led to the death of another health worker today,” WHO chief Tedros Adhanom Ghebreyesus said in a statement published on X on Sunday.
The paramedic was killed in an attack on an ambulance in the town of Bint Jbeil, while a medical warehouse was destroyed in an attack.
“Before today’s attacks, the WHO verified that 51 Lebanese health workers have been killed since March 2, including nine paramedics just yesterday.Tedros said.
“Attacks on healthcare facilities must stop immediately. This cannot become the norm..”