A former USA intelligence official has offered his nation's condolences to three Australians killed in attacks in London and Melbourne, Australia.

British police hunting for a Frenchman missing since Saturday's attack said earlier that they had found a body in the River Thames.

Experts suggested protocol may have tightened after leaks to the USA media about the Manchester attack.

Alexandre Pigeard (27), was among those killed, the French embassy confirmed.

Pigeard's dad described his son's death as an "incredible injustice", describing him as a "wonderful son, a ideal big brother", and a "shining young man", the Telegraph reported.

Brittany news outlet Le Telegramme reported an account from Boro Bistro manager Vincent Le Berre, who told how his colleague, Mr Pigeard, was attacked by a terrorist in the bar near Borough Market on Saturday night.

Her aunt, Tara, says Zelenak's mother Julie Wallace broke down when she learned of her daughter's death while travelling to Britain.

"I managed to escape him, but my friend Alexandre did not have that chance", he said.

"Sara's family and friends are devastated". "He was hit in the neck with a knife".

South Australian nurse Ms Boden - said to have run back towards danger to help the victims - was confirmed dead by her family on Wednesday night.

She was working as an au pair in London, and was seen fleeing from the knifemen during the attack.

Australian Sara Zelenak was a victim of the London attack.

Mr Echeverria, 39, (below) bravely tried to fight off one of the three terrorists with his skateboard as he helped an injured woman.

The Spanish foreign ministry confirmed the death yesterday, saying: "The exemplary attitude of Ignacio Echeverria during the attacks is, for everybody, a model of solidarity".

Police said the body had not been formally identified but that they have been searching for Xavier Thomas, 45, a French national who has been missing since the night of the attack.