A friend of Australian aid worker Zomi Frankcom, who was killed while working in Gaza by a reported Israeli air strike, says the woman was "huge-hearted" and "relentless" in her efforts to help others.

Four aid workers including Ms Frankcom and a Palestinian driver were killed while helping to deliver food and other supplies to northern Gaza through charity group World Central Kitchen (WCK).

The federal government has demanded an explanation from Israel, and called in Israel's ambassador to justify what Prime Minister Anthony Albanese has described as an "unacceptable" tragedy.

Ms Frankcom's friend and former WCK colleague Dora Weekley told the ABC her friend was "larger than life", and dedicated to aiding the most vulnerable.

"[Zomi] was just really dedicated and really driven, worked all hours and would put everything into it," Ms Weekley said.

"She was often doing community outreach and finding where the people in need were, and making sure they would have a hot meal every day to look forward to, and to give them some kind of hope for the future.

"She was on the front lines really of helping everyone in need."

Ms Weekley said she first met Ms Frankcom when the aid worker was responding to Hurricane Dorian after it swept through the Bahamas in 2019, and later worked with her again on the New South Wales south coast during the Black Summer bushfires.

After filmmaker Ron Howard directed an Emmy-nominated documentary on World Central Kitchen, Ms Frankcom was invited to walk the Emmys red carpet in Hollywood.

Ms Weekley said her friend told her to "hold on" to a photo of Ms Frankcom dressed up for the occasion, because it was rare for her to be dressed up and not deployed to provide relief.

"I remember getting a picture of her in a dress saying hold onto this forever because usually I'm in sweats and runners and I'm in Pakistan, or Afghanistan or, you know, she could be anywhere, and never with her hair done or make up done," Ms Weekley recalled.

"She worked all hours, she gave everything, and she believed in helping people who were less fortunate."

Ms Weekley said WCK colleagues she had spoken to were heartbroken.

"In a time of crisis you look to the helpers, and we've lost a really great one. A group of them," she said.

In a post on social media, WCK said the deaths were a tragedy.

"Humanitarian aid workers and civilians should NEVER be a target. EVER," the organisation wrote.