Newly released FBI files being reported by UK media show the US security authorities were concerned about "ever-present" threats to the late Queen Elizabeth II by the militant Irish Republican Army (IRA) during visits to America.

A memo warning US Federal Bureau of Investigation (FBI) agents in Boston and New York to remain "alert for any threats" ahead of a 1989 visit to the east coast of the country was among 102 pages of records released about the Queen who passed away aged 96 last September.

Other details include a police tip-off about a threat from an IRA sympathiser who wanted revenge for the death of his daughter.

According to ‘Sky News’, the officer who provided the information claimed that a month before then-US President Ronald Reagan and his wife Nancy Reagan hosted the Queen and husband Prince Philip in 1983, he received a phone call from a man he knew from an Irish pub. According to the memo, the man said his daughter was killed by a rubber bullet in Northern Ireland.

"This man additionally claimed that he was going to attempt to harm Queen Elizabeth and would do this either by dropping some object off the Golden Gate Bridge onto the royal yacht Britannia when it sails underneath or would attempt to kill Queen Elizabeth when she visited Yosemite National Park," the confidential file states.

The documents show FBI agents routinely shared intelligence and preparations with the US Secret Service about the IRA and its sympathisers during royal visits.

The FBI's concerns about potential IRA violence against members of the royal family were not unfounded. In 1979, Queen Elizabeth II's second cousin, Lord "Dickie" Mountbatten – the last viceroy of India, was killed in an IRA bombing in Ireland.

The records on threats to the late British monarch's life were released following a freedom of information request submitted after Queen Elizabeth II's death.

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