A relative of one of the five Australian-based journalists killed 40 years ago today in the town of Balibo in East Timor is calling for the Australian Federal Police to re-open its war crimes investigation into the deaths.

John Milkins, the son of the Channel 7 cameraman Gary Cunningham, said he wanted more information about why the AFP decided to close the investigation last year.

"I would be pleased to see it reopened," he said.

"I feel it was closed without an explanation to the Australian public."

Last night, as Mr Milkins prepared to take part in today's dawn service in Canberra commemorating the 40th anniversary of the deaths, he said there were still many unanswered questions about why the AFP decided to drop the investigation.

"We don't think that story's finished. I think perhaps the Government would like the book to be completely closed but I think there are many chapters still to write, there are many unknowns," he said.

But in a statement, the AFP said an extensive review of its investigation found there was insufficient evidence.

It said it had not received any new evidence to warrant reopening the case.

'They were there to break the silence but they were silenced'

The morning's service for the five Australian-based newsmen — Greg Shackleton, Gary Cunningham, Tony Stewart from Channel Seven and Malcolm Rennie and Brian Peters from Channel Nine — was held at the War Correspondents' Memorial of the Australian War Memorial in Canberra.

Organisers also planned to honour another Australian journalist, Roger East, who was killed on the Dili wharf after Indonesia invaded East Timor in December 1975.

Representatives from the East Timorese community, colleagues of the journalists and operators, Independent South Australian senator Nick Xenophon and family members of the Balibo Five gathered for the service.

Shirley Shackleton, the wife of Greg Shackleton, travelled from her home in Melbourne to speak at the service and lay wreaths for the victims on the new memorial.

"They were there [Balibo] to break the silence but they were silenced," Ms Shackleton said.

"These men were butchered as if they were cattle and they were just doing their job."

Musician Paulie Stewart was the brother of sound recordist Tony Stewart, who was 21 when he died.

He performed an uplifting and haunting song he co-wrote in the late 90s called Liberdade, which means liberty in Portuguese.

"I still find it hard to talk about. It's a very emotional day for me, I can't believe the white rage that this issue still fills me with," he said.

Shirley Shackleton spoke at the service and laid wreaths for the victims. ( ABC News: Adrienne Francis )

NSW coroner found Five were deliberately killed by special forces

The Media, Entertainment and Arts Alliance (MEAA) said it would commemorate the 40th anniversary by setting up a permanent scholarship to develop East Timorese journalists — the Balibo Five-Roger East scholarship.

MEAA chief executive officer Paul Murphy said it was an appalling example of impunity that no-one had faced justice over the deaths of the Balibo Five.

"The five journalists were upholding their profession's finest traditions in reporting to the rest of the world the threat of invasion of East Timor," he said.

In 2007, a NSW coroner found the Balibo Five had not been caught in crossfire but had been deliberately killed by Indonesian special forces who had attacked Balibo.

She referred the case to federal authorities for possible war crimes prosecutions.

The following year, the AFP began a war crimes investigation but last year it decided to drop the case, saying there were problems establishing jurisdiction and insufficient evidence to prove an offence.

Mr Milkins said he was concerned the AFP had not done enough to seek cooperation from Indonesia.

Representatives from the East Timorese community and colleagues and family members of the Balibo Five gathered for the service. ( ABC News: Adrienne Francis )

Senator Xenophon urged the AFP to consider reopening the case.

"I would like the AFP to re-look at the issue of the legal advice that they obtained and to see if there are any alternative avenues for prosecution," he said.

"Of course we cooperate with our Indonesian friends on a whole range of jurisdictional issues in fighting crime and terrorism.

"This was a war crime and it needs to be prosecuted and until it is the families of the Balibo Five won't have any sense of closure."

Mr Milkins said he and his relatives used a Freedom of Information request to seek more information about why the investigation had been dropped but he said that application had been rejected.

'We'll keep asking questions'

Mr Milkins said he had found some comfort through his connections with people in East Timor, many of whom lost multiple family members after the Indonesian invasion in December 1975.

"It's extraordinarily humbling to be standing in the main square of Balibo and to meet people who say 'your father was a martyr, we are so grateful for what he was trying to do' and then to talk to them for a while and discover they've lost eight members of their own family," he said.

As the secretary of a charity, the Balibo House Trust, he has worked on health and development projects for people in the Balibo region.

"That really is the light in the darkness, that's why it's better to look forward, but I'm not ever going to be able to say it's enough," he said.

"We'll keep asking questions until no more questions can be asked, on behalf of my relatives but on behalf of the Timorese who've said 'please keep asking'."

The AFP said it sympathised with the families of the Balibo Five as they commemorated the 40th anniversary of the deaths.