UN officials said that the monitors made ten phone calls to the Israeli army between 1.20pm on Tuesday — when an Israeli aircraft dropped a bomb 300 metres from the patrol base — and about 7.20pm, when the building was destroyed.

The details came to light as Kofi Annan, the UN Secretary-General, condemned what he called an “apparently deliberate targeting” of the well- documented UN position that had stood in Khiam, southern Lebanon, for 50 years.

All the dead were part of the Observer Group — Lebanon, which works with the UN Interim Force in Lebanon (Unifil).

Amid increasing international protest, Ehud Olmert, the Israeli Prime Minister, expressed deep sorrow for the deaths of the four unarmed officers from China, Finland, Canada and Austria.

Tzipi Livni, his Foreign Minister, rejected any suggestion of a deliberate attack, describing it as unfortunate. She said: “During a war these kind of accidents can happen.”

She made clear that the bombings would continue. “Israel can continue this operation if needed in order to target Hezbollah.”

Senior UN officials and foreign diplomats said that in the hours before the deaths warning calls came from as far afield as New York. They also said that Israeli forces fired on rescue vehicles sent to recover the bodies. “The bombs were falling on the heads of our guys for six hours,” a Unifil officer told The Times. “We kept telling the Israelis that our men had been lucky so far, but next time there was going to be a tragedy and could they please correct their targeting. We were begging them to stop.”

The Irish Republic filed an official protest with Israel, in which it said that Lieutenant-Colonel John Molloy, its senior Lebanon peacekeeper and a key UN figure liaising with the Israel Defence Forces, had given six specific phone warnings about the Khiam post.

“He warned the Israelis that they were shelling in very close proximity to the post, and his warnings were very specific, explicit, detailed and stark,” said Suzanne Coogan, a spokeswoman for Willie O’Dea, the Irish Defence Minister. “Obviously those warnings went unheeded.”

Jane Lute, the UN Assistant Secretary-General for Peacekeeping, told the Security Council that the post, which is three miles (5km) from an Israeli artillery position, came under close fire 21 times on Tuesday, suffering 12 hits within 100 metres and four direct hits. Contact was lost with the four peacekeepers inside at 7.17pm Ms Lute said that she and Mark Malloch Brown, the Deputy Secretary-General, called Israel’s mission to the UN in New York “reiterating these protests and calling for an abatement of the shelling”.

She said that Unifil secured safe passage for two armoured personnel carriers, which arrived at 9.30pm and found the shelter collapsed and severe damage to the rest of the position. Despite the agreement, she said, Israel attacked the carriers.

Dermot Ahern, the Irish Foreign Minister, said that Israeli troops fired on the Egyptian UN soldiers sent to dig out the bodies. “(It) raises questions about whether this was an accident,” he said.

Israel’s Ambassador to Beijing was summoned by China’s Foreign Ministry and asked to convey China’s request that Israel investigate the incident. “We are deeply shocked,” said Liu Jianchao, a spokesman for the Chinese Foreign Ministry.

The deaths are certain to hamper efforts to put together a multinational force to replace Unifil, which has long had a stormy relationship with Israel.

Unifil has 1,991 troops assisted by 50 military observers, but has been the subject of angry exchanges with Israel about its effectiveness in the past six years as Hezbollah established control over southern Lebanon.

An Israeli official recently told The Times that Unifil had a “co-operative relationship with Hezbollah”. However, UN personnel in Lebanon said that the bombing was merely the latest in a long history of Israeli attacks against its peacekeepers and observers.

In the past three days UN observers have reported frequent attacks close to their positions.

Heavy shelling around Khiam on Tuesday had forced the four observers into the bomb shelters. At about 1.20pm, officials say, a jet dropped a bomb only 300 metres away. The observers contacted the Unifil headquarters.

The observers warned Israel that their aircraft were dropping bombs dangerously close to a UN position. The Israelis said that they would check the situation and make any necessary adjustments, UN officials say. But jets then dropped ten bombs between 100 and 300 metres from the UN position and fired 12 artillery rounds within 150 metres, UN officials said. The fatal strike — using a “precision-guided weapon”, said UN military personnel — hit the post at about 7.20pm.

The Israel Defence Forces last night admitted responsibility for an “unintentional” strike. It said it was investigating.

• Twenty-four Palestinians, including 12 militants, two children and their mother, were killed yesterday by Israeli forces in Gaza.

  THE MONITORS

  UN Truce Supervision Organisation (UNTSO):

  UN Interim Force In Lebanon (Unifil)

• Fatalities: 249

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