Angry United Nations officials said Israel continued firing on the post as a rescue mission was begun to free two UN peacekeepers trapped under the rubble.

Tel Aviv is facing growing international pressure over the 300-plus civilians killed during its offensive against Hezbollah.

Israel denied aiming at the UN building and launched an investigation into yesterday's barrage. Israel Prime Minister Ehud Olmert said he had spoken to Mr Annan to express deep sorrow over the killings. Mr Olmert said he would order an investigation.

Mr Annan said the post, located in Khiam on the eastern Israeli-Lebanese border, had been there for a long time and was clearly marked.

"I am shocked and deeply distressed by the apparently deliberate targeting by Israeli Defence Forces of a UN observer post in southern Lebanon," Mr Annan said.

"This co-ordinated artillery and aerial attack on a long-established and clearly marked UN post at Khiam occurred despite personal assurances given to me by Prime Minister Ehud Olmert that UN positions would be spared Israeli fire.

"I call on the Government of Israel to conduct a full investigation into this very disturbing incident and demand any further attack on UN positions and personnel must stop."

Herald Sun-AU