Multiple aid workers were killed after a bus was attacked in Gaza on Wednesday night, according to a US-backed humanitarian aid organization which accused Hamas of carrying out the assault.

The war began when Hamas-led militants killed around 1,200 people, mostly civilians, in the Oct. 7 attack and abducted 251 hostages. More than half the captives have been released in ceasefires or other deals. Israeli forces have rescued eight and recovered the remains of dozens more.

The group, which has been harshly criticized by the U.N. and other aid providers, said at least five people had died in an attack on one of its buses.