The killing of seven aid workers in an Israeli air strike on Gaza shows no one in the region is safe, the founder of a New Zealand aid organisation says.
Israel is facing criticism from its allies after its killing of the seven World Central Kitchen (WCK) aid workers.
Israel's Prime Minister Benjamin Netanyahu has acknowledged the Israeli military hit "innocent people", describing it as tragic and unintentional.
However, WCK founder Jose Andres told Reuters the charity group he founded had clear communication with the Israeli military, which he said knew his aid workers' movements.
"This was not just a bad luck situation where 'oops' we dropped the bomb in the wrong place," Andres said.
Mike Seawright, of New Zealand group Relief Aid - which itself had two staff members killed when their homes were bombed in November - said the latest aid worker deaths had his staff in Gaza feeling very worried.
"They had assumed, despite what recent facts have shown them, that being a humanitarian organisation, being an aid worker would offer some protection."
The attacks against WCK staff had proved that was not the case, and Seawright said Relief Aid staff were "very worried that they'll get hurt or killed just delivering aid".
Ensuring the security of aid workers and NGO staff was a technical matter, and there was an acceptance it was impossible to completely eliminate risk, he said.
"We talk about things like deconfliction - this is where we will tell the warring parties where our offices are, where our vehicles are moving, where the hospitals are. Unfortunately, as again we're seeing with these recent attacks, these are offering little or no protection because World Central Kitchen follows much the same protocols that Relief Aid does and in fact that didn't help them."
He said people in Gaza were "desperate for food" and even experienced aid workers were finding the situation on the ground there very challenging.
"When you're working in these environments, it's extremely hard, despite the fact that you may be experienced in operating in these sorts of environments; it's extremely hard to see people in such difficult and dire circumstances."
Relief Aid was taking a "low-visibility approach" in Gaza to try and reduce risk, he said, including by using smaller vehicles to distribute aid rather than larger trucks which could attract attention.
But Seawright said a ceasefire was imperative to allow much-needed aid in over the border from Egypt.
"What we absolutely must do is have a ceasefire. We must have unfettered access for humanitarian workers and humanitarian organisations to Gaza now."
The flow of weapons into the region also needed to be stopped, he said.
"It beggars belief that we have governments, such as the UK and the US calling for a ceasefire, calling for civilians not to be hurt, and yet continuing to export arms out of their countries to Israel."