Australian Kirsty Boden is feared to be among the victims of the London attacks.

A second Australian feared killed in the London terrorist attack has been named in media reports as former South Australian woman Kirsty Boden.

Ms Boden, 28, was a health professional who had lived in London for some time, the Nine Network reported on Tuesday.

SA Premier Jay Weatherill said it was a matter for commonwealth authorities to confirm the identity of the second Australian of concern.

But he said the state government was “putting in place all the appropriate measures to provide support for the families that are associated with this particular notification”.

The woman’s family in Loxton, in SA’s Riverland region, told AAP “there’ll be no comment at this time”.

It was unclear if Ms Boden was hurt when terrorists used a van to run down pedestrians on London Bridge or when they went on a stabbing rampage in a nearby market.

There were unconfirmed reports the nurse may have been attempting to assist another person.

Prime Minister Malcolm Turnbull said there were real concerns about the two Australians after the weekend attack in which seven people were killed and 48 injured.

“We are working diligently in London with the police and other authorities there and, of course, staying in very close contact with their families as we seek to confirm the circumstances relating to those two Australians,” he told reporters in Canberra on Tuesday.

Australian authorities are also working with British police to establish the whereabouts of Brisbane woman Sara Zelenak, who is still missing after being separated from friends on London Bridge at the time of the attack.

A Facebook post by a family friend shared hundreds of times on Monday appealed for information about the 21-year-old, saying she usually rang her mother daily.

As fears grew for Ms Boden, a Facebook post by Sarah Recchia described her as “one of the nicest people you’d ever meet”.

Ms Boden went to Loxton High School and graduated from Flinders University in Adelaide.

She was a talented swimmer in her youth, at one stage holding a number of age-group records at an Adelaide swimming club.