Fears are growing for missing Brisbane woman Sara Zelenak who became separated from friends at the scene of the London terror attack.
The 21-year-old's mother, Julie Wallace, is on her way to London while a GoFundMe page has raised more than $12,000 to help the family with the search.
Ms Zelenak has been missing since the London Bridge attacks on Sunday (AEST).
Ms Zelenak was working as an au pair and Ms Wallace says her daughter had been given the night off so she could go out with a friend.
"She was heading for the London Bridge where everyone goes on a Saturday night," Ms Wallace told Brisbane's 4KQ.
Ms Zelenak's friend Pri Goncalves says they became separated on the London Bridge when the attacks started.
Missing Brisbane woman Sara Zelenak Source: Facebook
"Sara was with me when people started running and shouting but at that very moment we got separated," she told Fairfax.
Ms Goncalves says she has been desperately trying to contact Sara since they were separated.
"When I was close to Borough Market I saw a guy on top of another guy who was screaming and then I knew something really bad was happening. I think he was stabbing him," she said.
"So I started calling her (Sara) but she never picked up the phone."
'I feel terrible, I can't think'
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.
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 reporting 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.
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 in London told AAP that 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."
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.
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 Zelenac came as the Queensland families of two other Australians - Brisbane's Candice Hedge and Darwin electrician Andrew Morrison - took comfort in news they were okay.
Ms Hedge, 34, working as a waitress in the Borough Markets 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, told AAP 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 on Tuesday 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 told reporters "it could have been worse, a lot worse".
Prime Minister Malcolm Turnbull said on Monday the government had "very real concerns" for two other unnamed Australians.
He would not divulge details and it's not known if one of them is Ms Zelenak.
"This is the work of cowardly, crazed criminals," Mr Turnbull said of the terror attack to reporters in Sydney.
