In a statement released by his spokesman, Annan, who is attending an international meeting in Rome on the situation in the Middle East, said "this coordinated artillery and aerial attack" occurred despite personal assurances given to him by Israeli Prime Minister Ehud Olmert that UN positions would be spared fire.

He further pointed out that the post, near the Lebanese town of Khiyam, was "long established and clearly marked."

"Furthermore, General Alain Pelligrini, the UN Force Commander in south Lebanon, had been in repeated contact with Israeli officers throughout the day on Tuesday, stressing the need to protect that particular UN position from attack," the UN chief added.

Annan thus called on the government of Israel to conduct a full investigation into this very disturbing incident, and demanded that any further attack on UN positions and personnel must stop.

He said that the names and nationalities of the fallen peacekeepers were being withheld pending notification of their families, to whom he extended his condolences.