Human Rights Watch and others say they have documented use of weapon in civilian areas, which some argue is illegal

When the M825-series 155mm artillery projectile airbursts, expelling its felt wedges containing white phosphorus, it leaves a distinctive knuckle-shaped plume. That is how Human Rights Watch (HRW) researchers said they were able to verify that Israel was again using the notorious weapon over south Lebanon, reigniting accusations that it is breaking the laws of war.

The New York-based rights group said it had verified and geolocated eight images showing airburst white phosphorus munitions exploding over residential areas in the southern Lebanese town of Yohmor in the opening days of Israel’s assault during the war on Gaza.

Since then, more videos have emerged purporting to show white phosphorus munitions exploding over south Lebanon, and researchers say that with 800,000 Lebanese people displaced from the region after Israeli forces ordered them to leave, many more uses may have gone undocumented.

In the last week, Israeli soldiers have been facing fierce resistance from Hezbollah fighters in south Lebanon, despite an intense bombing campaign. In recent days, Israeli forces have bombed roads, petrol stations, bridges and medical centres in an effort to cut south Lebanon off from the rest of the country.