A human rights group says the Israeli air strike on Qana that killed 54 civilians is a "war crime".
Most of the victims in Qana were children
Human Rights Watch accused the Israeli Defence Forces (IDF) of treating southern Lebanon as a "free-fire zone".
It said the failure to distinguish between civilians and combatants could be judged as a war crime, and called for an UN probe into the conflict.
Israel has insisted that Hezbollah sheltered in Qana and used it as a base to fire rockets across the border.
But Human Rights Watch called on a UN commission to investigate whether serious violations of international law had taken place during the conflict.
"The Israeli military seems to consider anyone left in the area a combatant who is fair game for attack," said Kenneth Roth, executive director of Human Rights Watch.
"Such consistent failure to distinguish combatants and civilians is a war crime."
The Israeli air strike on the southern Lebanese village of Qana in the early hours of Sunday killed at least 54 Lebanese civilians, mostly children.
The bombing has prompted international outrage and urgent diplomacy to bring about a ceasefire between Israel and militant group Hezbollah.
The IDF said in a statement that Qana had been used since the beginning of events as a "hideout" and a place from where approximately 150 rockets had been fired into Israel.
The IDF also said that residents in the village and surrounding areas were warned in advance to stay out of areas where rockets were being launched at Israel.
"Even after this tragic event, the circumstances of which are still being investigated, we appeal to the residents of southern Lebanon to distance themselves from terrorists, to distance themselves from launch areas, for their own safety," said Maj Gen Gadi Eizenkot.
The UN's emergency relief co-ordinator was highly critical of Israel's strike in Qana, calling it "indiscriminate and excessive".
But Jan Egeland refused to absolve Hezbollah of a share of the blame, reminding the group that using civilian areas as a base for military operations had long been "illegal and immoral".
"It has been so for 100 years, simply for the very reason that you make the women and children as much a target as you are yourself," Mr Egeland said.
However, Human Rights Watch said responsibility for Qana rested "squarely with the Israeli military".
"Just because the Israeli military warned the civilians of Qana to leave does not give it carte blanche to blindly attack," said Mr Roth. "It still must make every possible effort to target only genuine combatants."
[Note: The number of people killed in the Israeli bombing of Qana was later revised. The Washington based human rights group Human Rights Watch investigated the incident and issued a report on 3 August saying that 28 people were known to have died, while 13 people were missing.]