The Vietnamese Government appears to have reneged on a deal to allow veterans and their families to visit the Long Tan memorial cross, with Australians turned away from the site by local police.

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Those turned away included Harry Smith, the commander of D Company, which fought the battle at Long Tan exactly 50 years ago.

Visitors at the site reported long queues of people trying to get near the former battlefield.

Some people were allowed to visit the cross after waits of around three hours, but were only allowed one minute at the memorial site. A Vietnamese source said police were concerned about security.

Nine Long Tan veterans instead attended a private indoor memorial service, which included the Last Post and the Ode, back at their hotel.

Former veterans from both sides also gathered for a Friendship Dinner in Vung Tau, which included Mr Smith and Victoria Cross recipient Keith Payne.

Mr Smith said he had been disappointed to be turned away from the ceremony, but not surprised.

"It was mentioned some weeks ago when I was in Canberra that Hanoi was a bit worried about the number of people expected , like 3,000, and it was all getting too much, too big, getting out of hand," he said.

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More than 1,000 Australians travelled to Vietnam to mark the anniversary, but the Vietnamese Government cancelled the main memorial event.

A Vietnamese Government source told the ABC the Australian Consulate had promised to hold a "low key" event, but that a planned gala dinner and concert were seen as insensitive.

On Wednesday night Prime Minister Malcolm Turnbull and his Vietnamese counterpart reached a compromise.

A key element of the deal was access to the Long Tan cross, but it appears this has been ignored.

The Long Tan anniversary is a contentious topic in Vietnam, and visitors to the Battle of Long Tan site are not allowed to wear medals or uniforms, carry banners or make speeches.

In recent years, the playing of The Last Post has been allowed.

After the compromise deal was announced, Veterans' Affairs Minister Dan Tehan said he was glad for the reprieve.

On Thursday night he told 7.30 a plan for future years needed to be sorted out.

"I think it's very important that we get an understanding on both sides about what are the requirements for us to be able to continue to go to Vietnam to commemorate the Battle of Long Tan and also Vietnam veterans' day," he said.

Australians queued for three hours at the entrance to Long Tan. ( Supplied )

Meanwhile, services were held around Australia to mark the battle's 50th anniversary.

They included an early morning service at the War Memorial in Canberra, where the names of the those killed in the Vietnam war were projected onto the building's exterior.

According to the Department of Veterans' Affairs, 18 Australians were killed in the Battle of Long Tan, with another 24 wounded.

Australian forces counted 245 dead Vietnamese.

Mr Tehan told 7.30 Vietnam veterans were unique among returned service personnel.

"They went, they fought but it was the welcome home which really in many ways set them apart," he said.

"They weren't welcomed like previous generations had, and that left a scar which only today we're beginning to properly heal."

A commemorative service at the Long Tan Cross in 1969. ( Australian War Memorial )

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