Visiting UN chief Ban Ki-moon met the commander of the peacekeeping force in southern Lebanon on Saturday and paid tribute to fallen soldiers.
Ban, who is on a three-day visit to Lebanon, travelled by helicopter to the town of Naqura, headquarters of the United Nations Interim Force in Lebanon (UNIFIL).
He laid a wreath and observed a minute of silence at a memorial site for the 293 peacekeepers who have died in Lebanon since the creation of UNIFIL in 1978.
"Peace-keeping is always dangerous but it is especially deadly in Lebanon," he said in a brief speech.
"More personnel have lost their lives serving in UNIFIL than in any other United Nations peacekeeping operation," he added. "This weighs heavily on my heart."
UNIFIL soldiers have been the target of three attacks in the past year that have prompted fears they could be linked to the deadly unrest in neighbouring Syria.
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Ban said he had stressed in his meetings with Lebanese officials on Friday that the safety of UNIFIL personnel was "critically important" and had called for strenghthening security for UNIFIL.
The force was deployed in 1978 to maintain stability at the border between Lebanon and Israel.
It was expanded in 2006 following a devastating war between the Shiite militant group Hezbollah and the Jewish state. It now numbers some 12,000 troops from 35 countries.
Ban met with Major General Alberto Asarta Cuevas, the head of UNIFIL, who briefed him on the force's operations in the south.
He was also meeting in Beirut with members of the Western-backed opposition and other officials.
He was to hold talks in the evening with Turkish Foreign Minister Ahmet Davutoglu, who is traveling to Beirut to attend a UN conference on the transition to democracy in the Arab world.
On Sunday, Ban is to give the keynote address at the two-day conference's opening ceremony.