Fears are growing for missing Brisbane woman Sara Zelenak, who became separated from friends at the scene of the London terror attack.

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

Ms Zelenak's stepfather Mark Wallace said from Brisbane that UK authorities had been unable to shed any light on where she was following the attack on Sunday morning (AEST).

“I feel terrible, I can't think,” News Corp reported him saying.

“I've contacted every hospital in London but they can't give out patient details or even tell us if she has been admitted,” he said.

Sara Zelenak has not been heard from since the attack. (Supplied)

A Go Fund Me page has been set up by friends of the Wallace family who are trying to raise $15,000 help them search for her.

“The funds raised will be used to get her mum and dad from Australia to London and accommodate them while they continues to search for their beautiful daughter,” the family friend wrote.

So far $13,032 has been raised, but speaking with Brisbane radio station 97.3FM this morning Ms Zelenak's mother, Julie, said British police told them to wait another 24 hours before heading to the UK.

Ms Zelenak's friend Pri Gonçalves, 26, is desperate searching for her in London.

“Please help, I just want to find her, she is an amazing person and it's just not fair that something bad might have happened to her,” Ms Gonçalves told the Brisbane Times .

“I wasn't able to help her and it's killing me.

“We were having fun that day, she has plans and all I want is for her to achieve them all.”

Ms Zelenak had moved to London in March to work as an au pair.

Mr Wallace said she had been planning to babysit the night of the attacks but at the last minute the children's grandmother stepped in so she went out with friends.

A Metropolitan Police spokesman said police had not yet released the names of the dead or injured and he could not help with a specific inquiry about Ms Zelenak.

“We are trying to locate people as best we can,” he said.

The spokesman said a casualty bureau had been set up to assist people trying to find family members who may have been caught up in the attacks.

Candice Hedge was stabbed in the neck and has undergone surgery. (Supplied)

Andrew Morrison. (Facebook)

Seven people were killed and 48 wounded when three men launched the attack just after 10pm on Saturday local time.

Police shot the three terrorists dead within eight minutes of the violence erupting.

The frantic appeal for Ms Zelenak came as the Queensland families of two other Australians - Brisbane's Candice Hedge and Darwin electrician Andrew Morrison - took comfort in news they were OK.

Ms Hedge, 34, working as a waitress in the Borough Market area, underwent emergency surgery but is expected to make a full recovery after her attackers missed her windpipe and arteries.

“She can't think how she got so lucky because she thought she was going to die,” her grandfather Brian, who lives in Queensland's Darling Downs, said after speaking to her by phone on Monday morning.

“She said 'grandad you know I'm a Hedge and I'm a fighter, I'll get over this,” he said.

Mr Morrison is on his way home and due to land today, after receiving stitches for a stab wound he received while leaving a bar after watching the Champions League soccer final.

He said he believed a brawl was breaking out when “all of a sudden a guy comes up with a knife ... stabs me there (motioning to his neck) I push him off and blood is going everywhere”.

Mr Morrison's Gold Coast-based father Dave has said “it could have been worse, a lot worse”.

Prime Minister Malcolm Turnbull yesterday said the government had "very real concerns" for two other unnamed Australians.

He would not divulge details and it is not known if one of them is Ms Zelenak.

“This is the work of cowardly, crazed criminals,” Mr Turnbull said of the terror attack.

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