Human Rights Watch on Thursday accused Israel of using white phosphorus munitions in its military operations in Gaza and Lebanon, saying the use of such weapons puts civilians at risk of serious and long-term injury.

In an apparent rebuttal, the Israeli military said in a statement: "The current accusation made against the IDF (Israel Defense Force) regarding the use of white phosphorus in Gaza is unequivocally false.

"The IDF has not deployed the use of such munitions," it added. It was not immediately clear whether the latter statement also applied to Lebanon.

Israel has been bombarding Gaza in retaliation for a Hamas rampage in southern Israeli towns that killed at least 1,300 people this week. At least 1,500 Palestinians have been killed. Israel has also traded barbs with Lebanon's Hezbollah group.

Human Rights Watch said it verified videos taken in Lebanon on Oct. 10 and Gaza on Oct. 11 showing "multiple airbursts of artillery-fired white phosphorus over the Gaza City port and two rural locations along the Israel-Lebanon border".

It provided links to two videos posted on social media that it said show "155mm white phosphorus artillery projectiles being used, apparently as smokescreens, marking, or signaling". Both show scenes near the Israel-Lebanon border, it said.

The group did not provide links to videos showing their alleged use in Gaza. Palestinian TV channels have broadcast video in recent days showing thin plumes of white smoke lining the sky over Gaza that they say was caused by such munitions.

Reuters could not independently verify the rights group's accounts.

Israel's military in 2013 said it was phasing out white phosphorus smokescreen munitions used during its 2008-2009 offensive in Gaza, which drew war crimes allegations from various rights groups.

The military at the time did not say whether it would also review use of weaponized white phosphorus, which is designed to incinerate enemy positions.

White phosphorus munitions can legally be used on battlefields to make smoke screens, generate illumination, mark targets or burn bunkers and buildings.

Because it has legal uses, white phosphorus is not banned as a chemical weapon under international conventions, but it can cause serious burns and start fires.

White phosphorus is considered an incendiary weapon under Protocol III of the Convention on the Prohibition of Use of Certain Conventional Weapons. The protocol prohibits using incendiary weapons against military targets located among civilians, although Israel has not signed it and is not bound by it.