image sourceReutersimage captionThe 13-storey Hanadi tower in Gaza City was destroyed in an air strike on 11 May

Israeli air strikes that destroyed four high-rise buildings during May's conflict in the Gaza Strip may amount to war crimes, campaign group Human Rights Watch (HRW) says.

No-one was hurt in the attacks, but a report says several dozen families were left homeless and buildings damaged.

Israeli authorities said at the time that Palestinian militant groups were using the towers for military purposes.

But HRW said they had provided no evidence to support those allegations.

At least 256 people were killed in Gaza, according to the United Nations, and 13 people were killed in Israel during 11 days of fierce fighting.

It began after weeks of spiralling Israeli-Palestinian tension in East Jerusalem which culminated in clashes at a holy site revered by both Muslims and Jews. Hamas – the militant Islamist group which rules Gaza – began firing rockets after warning Israel to withdraw from the site, triggering retaliatory air strikes.

image sourceAFPimage captionHuman Rights Watch has said the firing of rockets by Palestinians towards Israeli civilians amounted to war crimes

Between 11 and 15 May, Israeli strikes destroyed the Hanadi, Jawhara, Shorouk, and Jala towers in Gaza City.

In each case, the Israeli military warned tenants of impending attacks, allowing for their evacuation, according to HRW's report.

Israeli authorities said the buildings housed offices of Hamas and other Palestinian militant groups, including the headquarters of certain units and military intelligence. One tower included offices for "the most valuable Hamas technological equipment" for use against Israel, it says.

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HRW's investigation was based on interviews with 18 Palestinians who witnessed the strikes or were affected by them, along with analysis of videos and photographs.

It found no evidence that members of militant groups involved in military operations had a current or long-term presence in any of the towers at the time they were attacked.

Even if there were such a presence, the report says, the attacks appeared to cause foreseeably disproportionate harm to civilian property.

media captionThe Gaza tower block housing news outlets destroyed in an Israeli strike

The strike on the 12-storey Jala Tower, which housed the offices of the Associated Press (AP) news agency and the Al Jazeera broadcasting network, provoked widespread outrage.

In June, Israel's ambassador to the US told AP executives that the building was being used by Hamas to develop an electronic jamming system against the Israeli military's Iron Dome missile defence system.

But the AP's executive editor said it had never had any indication that Hamas militants might be in the tower.

"The apparently unlawful Israeli strikes on four high-rise towers in Gaza City caused serious, lasting harm for countless Palestinians who lived, worked, shopped, or benefitted from businesses based there," said Richard Weir, HRW's crisis and conflict researcher. "The Israeli military should publicly produce the evidence that it says it relied on to carry out these attacks."

The Israeli military has not yet commented on the report, but it has previously accused Palestinian militants of deploying among civilians and using them as human shields, which would be a war crime.

HRW has published two other reports on the conflict that accused both sides of carrying out attacks that apparently amount to war crimes.

The first said an investigation into three Israeli strikes that killed 62 civilians found no evidence of military targets nearby, while the second said the firing of 4,000 unguided rockets and mortars towards Israeli cities and towns by Palestinian militants constituted indiscriminate attacks on civilians. Both the Israeli military and Hamas denied the accusations.