There was fierce fighting in the Khiam area for six hours

According to diplomats familiar with the UN's initial report into the incident, the post in the town of Khiam was hit by precision-guided munition, says the BBC's Paul Adams in Jerusalem.

The report says there was fierce fighting in the area for about six hours before the post was hit, during which time UN personnel contacted the Israel military 10 times, urging them to stop firing.

Our correspondent says the UN claims that after each call, it was assured the firing would stop.

Six warning calls

A preliminary UN report said 17 bombardments landed within one kilometre of the post, and 12 artillery rounds hit within 150 metres of the structure - four of them being direct hits.

After this, the post was hit by a precision-guided weapon from an Israeli aircraft.

The Irish foreign ministry said one of its officers in the UN's Unifil peacekeeping force in south Lebanon, placed six warning calls to the Israel Defence Forces (IDF) prior to the attack.

"On six separate occasions he was in contact with the Israelis to warn them that their bombardment was endangering the lives of UN staff in South Lebanon," Reuters news agency quoted an unnamed foreign office spokesman as saying.

"He warned: 'You have to address this problem or lives may be lost'," the spokesman said.

The Associated Press news agency named the officer as Lt Col John Molloy.

The bomb which killed the unarmed peacekeepers - Canadian, Austrian, Finnish and Chinese soldiers - hit the building and shelter of the observation post, near the eastern end of the Lebanese-Israeli border, UN spokesman Milos Struger said.

Israel has launched an investigation.

The UN post was on high ground, in an area once occupied by Israel.