In a statement released in Geneva, Arbour said Israeli had legitimate security concerns but needed to respect international humanitarian laws and refrain from attacking civilians and civilian objects.

A Lebanese soldier stands next to a crater following Israeli airstrikes at the main Mar Mikhail crossroads in southern Beirut, Lebanon, Friday, July 14, 2006. Israel has widened its offensive on Lebanon, with fighter bombers blasting the airport for a second day, residential buildings in the southern suburbs of the capital, igniting fuel storage tanks and cutting the main highway to Syria.[AP]

"In particular, they have an obligation to exercise precaution and to respect the proportionality principle in all military operations so as to prevent unnecessary suffering among the civilian population," the former Canadian Supreme Court judge said.

"The prohibition on targeting civilians is also being violated by Hizbollah," she said.

In a separate statement, the International Committee of the Red Cross (ICRC) urged Hizbollah militants to treat humanely the two Israeli soldiers they are holding and said it wanted access to them in order to assess their condition.

The Swiss-based humanitarian body also told Israel to show respect for ambulances and emergency workers using the Red Cross and Red Crescent symbols.

The ICRC said it was very concerned that Israel's establishment of a sea and air blockade on Lebanon would hurt the civilian population, and reminded all sides of the conflict that it is illegal to attack people not taking direct part in hostilities.

"All precautions must be taken to spare civilian life and property, and to ensure that the wounded have access to medical facilities," the ICRC declared.