The Marshall Islands on Saturday marked 60 years since the devastating US hydrogen bomb test at Bikini Atoll, with angry exiled residents saying they were too fearful to ever go home.

Part of the intense Cold War nuclear arms race, the 15-megaton Bravo test on March 1, 1954 was a thousand times more powerful than the atomic bomb dropped on Hiroshima.

It vaporised one island and exposed thousands in the surrounding area to radioactive fallout.

As those who remembered that terrifying day gathered in the Marshall Islands' capital of Majuro, along with younger generations, to commemorate the anniversary, many exiles refused to go back to the zones that were contaminated, despite US safety assurances.

"I won't move there," Evelyn Ralpho-Jeadrik, 33, said of her home atoll, Rongelap, which was engulfed in a snowstorm of fallout from Bravo and evacuated two days after the test. "I do not believe it's safe and I don't want to put my children at risk."

People returned to live on Rongelap in 1957 but fled again in 1985 amid fears, later proved correct, about residual radiation.

One of the more than 60 islands in Rongelap has been cleaned up as part of a US-funded $45 million programme, but Ralpho-Jeadrik said she has no intention of going back.

"I will be forever fearful. The US told my mother it was safe and they returned to Rongelap only to be contaminated again," she said.

It is not just their homes which have been lost, said Lani Kramer, 42, a councilwoman in Bikini's local government, but an entire swathe of the islands' culture.

"As a result of being displaced, we've lost our cultural heritage -- our traditional customs and skills, which for thousands of years were passed down from generation to generation," she said.

Bikini islanders have lived in exile since they were moved for the first weapons tests in 1946, when Kramer's own grandparents were evacuated.

When US government scientists declared Bikini safe for resettlement, some residents were allowed to return in the early 1970s.

But they were removed again in 1978 after ingesting high levels of radiation from eating local foods grown on the former nuclear test site.

"After they were exposed like that I can never trust what the US tells us (about Bikini)," said Kramer, adding that she wants justice for the generations forced to leave.

- 'The sky turned red' -

The Marshall Islands Nuclear Claims Tribunal had awarded more than $2 billion in personal injury and land damage claims arising form the nuclear tests, but stopped paying after a US-provided $150 million compensation fund was exhausted.

At a ceremony to mark the anniversary Saturday Marshall Islands President Christopher Loeak called on the US to resolve the "unfinished business" of its nuclear testing legacy, saying compensation provided by Washington "does not provide a fair and just settlement" for the damage caused.

US ambassador Thomas Armbruster said "words are insufficient to express the sadness" of the 60th anniversary of the nuclear test, adding that the United States is continuing to work with the Marshall Islands to provide health care and environmental monitoring of several affected islands.

The US embassy in Majuro said on its website: "While international scientists did study the effects of that accident on the human population unintentionally affected, the United States never intended for Marshallese to be hurt by the tests."

Also attending the week-long commemorations, which included a parade on Saturday, is 80-year-old Matashichi Oishi -- one of 23 fishermen aboard the Japanese Lucky Dragon boat, which was 100 kilometres (60 miles) from the bomb when the test occurred.

"I remember the brilliant flash in the west, the frightening sound that followed, and the extraordinary sky which turned red as far as I could see," he said.

The plight of the crew is well-known in Japan and on Saturday nearly 2,000 people marched to the grave of Aikichi Kuboyama -- the chief radioman of the boat -- in the port city of Yaizu, 170 kilometres southwest of Tokyo, to mark the anniversary.

Kuboyama died of acute organ malfunction nearly seven months after the test, while 15 other crew members later died of cancer and other causes.

US nuclear experiments in the Marshall Islands ended in 1958 after 67 tests.

But a United Nations report in 2012 said the effects were long-lasting.

Special Rapporteur Calin Georgescu, in a report to the UN Human Rights Council, said "near-irreversible environmental contamination" had led to the loss of livelihoods and many people continued to experience "indefinite displacement".

The report called for the US to provide extra compensation to settle claims by nuclear-affected Marshall islanders and end a "legacy of distrust".