UN peacekeepers in south Lebanon contacted Israeli troops 10 times before an Israeli bomb killed four of them, an initial UN report says.

The post was hit by a precision-guided missile after six hours of shelling, diplomats familiar with the probe say.

The four unarmed UN observers from Austria, Canada, China and Finland, died after their UN post in the town of Khiam was hit by an Israeli air strike on Tuesday.

The UN report says each time the UN contacted Israeli forces, they were assured the firing would stop.

A senior Irish soldier working for the UN forces had warned the Israelis six times that their bombardment was endangering the lives of UN staff, Ireland's foreign ministry said.

Had Israel responded to the requests, "rather than deliberately ignoring them", the observers would still be alive, a diplomat familiar with the report said.

This is really not good.