The US- and Israeli-backed Gaza Humanitarian Foundation said two American staff members were wounded Saturday in an attack on one of its aid centres in southern Gaza.
"This morning, two American aid workers were injured in a targeted terrorist attack during food distribution activities at SDS-3 in Khan Yunis," the organisation said in a statement, noting the employees were in stable condition.
"The attack -- which preliminary information indicates was carried out by two assailants who threw two grenades at the Americans -- occurred at the conclusion of an otherwise successful distribution in which thousands of Gazans safely received food," it added.
The Israeli military said in a statement it had evacuated the injured.
An officially private effort, the GHF began operations on May 26 after Israel halted supplies into the Gaza Strip for more than two months, sparking warnings of imminent famine.
GHF operations have been marred by chaotic scenes and near-daily reports of Israeli forces firing on people waiting to collect rations.
More than 500 people have been killed while waiting to access rations from its distribution sites, the UN Human Rights Office said Friday.
The Israeli military has blamed Hamas for the incidents.
"GHF has repeatedly warned of credible threats from Hamas, including explicit plans to target American personnel, Palestinian aid workers and the civilians who rely on our sites for food. Today's attack tragically affirms those warnings," the foundation said.