Thousands have turned out for a vigil to honour the victims of the London Bridge attack.
The family of an Australian woman caught up in London's terror attacks has confirmed she died "running towards danger".
South Australian nurse Kirsty Boden, 28, was on London Bridge when she was set upon by terrorists who carried out the attack that left seven people dead just after 10pm on Saturday, local time.
In a statement on Tuesday afternoon, Boden's family said she was "loved and adored by family, friends and her boyfriend.
"We love you and we miss you dearly," they said. "Helping people was what she loved to do in her job as a nurse and her daily life."
They said she ran towards where the attack had taken place to help others already injured.
"We are so proud of Kirsty's actions which demonstrate how selfless, caring and heroic she was. Not only on that night but throughout her life."
The young woman from Loxton, South Australia had previously written online about her love of travel on a blog "The Time Poor Traveller."
"I love to travel, although I am not a nomad, vagabond or wanderer. I have no plans to quit my job and travel the world taking selfies and instagramming my dinner. I'm just your average dreamer, with a full time job and a constant longing to go where I haven't been," she wrote, while posting pictures of her visits to cities in Europe and the UK.
The news comes as the third attacker has been named as Moroccan Italian, Yousseff Zaghba, 22, from East London. He was not known to police. Pakistan-born British citizen Khuram Shazad Butt, 27 and Rachid Redouane, 30, who claimed to be Moroccan and Libyan were also named on Monday.
Kirsty Boden of Loxton, South Australia. Photo/Facebook
Boden was reported as "missing" on Tuesday and it is understood she is the previously unidentified Australian that Prime Minister Malcolm Turnbull referred to during a press conference earlier today.
Australian authorities are still working with British police to establish the whereabouts of Brisbane woman Sara Zelenak, who was still missing after last being seen on London Bridge during the attack.
Her family are travelling to London and are said to be preparing for the worst after friends revealed she had not answered her phone or checked her Whatsapp messages since five minutes before the attack.
Friend Pri Goncalves called her at 10.09, 10.16pm and again 10.17pm - one minute after the attackers were shot dead - but received no answer. The messaging service shows she has not been online since 10.03pm and it is thought she may have dropped her phone in the panic.
Prime Minister Malcolm Turnbull said four Australians were believed to be caught up in the attack. Candice Hedge and Andrew Morrison were found to be recovering from serious injuries.
News.com.au understands hospitals can't give out any information to family members who call to inquire about missing loved ones because London is in a "terror lock down" and for privacy reasons.
South Australian Premier Jay Weatherill said it was a matter for commonwealth authorities to confirm the identity of the second Australian of concern but 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".
On Monday, a second victim of the attack was named by his family as James McMullan, 32.
His sister Melissa McMullan broke down in tears as she announced the news of her beloved brother's death and slammed the terrorists responsible.
"While our pain will never diminish. It is important for us to all carry on with our lives "Hatred is the refuge of small minded individuals and will only bring more.
"Words will never be able to match his essence. There will only ever be one James.
Nowhere else will you find such humour. He was an inspiration," she said, adding that the police would be unable to formally identify him until the coroners report tomorrow.
McMullan had not been seen since he stepped outside a pub for a cigarette onto London Bridge near where the van was later seen to have crashed.
The London Bridge attackers walk towards Borough Market. Photo / Supplied
Earlier, Melissa had pleaded for his safe return, saying: His family need him home x."
He's the second victim to be officially named after Canadian woman Christine Archibald who died on London Bridge.
Four people remain missing with family and friends leaving desperate pleas on social media to help find them.
Friends and family of a Brisbane woman, Sara Zelanak, 21 have also posted about fears for her safety, saying she became separated from friends and has not been seen since.
Her heartbroken stepfather Mark Wallace said his family hadn't heard from her for 48 hours and authorities hadn't been able to shed any light on where she was.
Spaniard Ignacio Echeverria, 39, has not been seen since he ran into help defend an injured woman and took on the attackers with his skateboard.
His brother Joaquin said the family had been asked to provide his fingerprints and fear the worst for him.
Frenchman Sebastian Belanger has also not been seen since Saturday. His girlfriend Gerada has launched appeals online asking "if anyone has seen him or knows anything contact me."
Another Frenchman, Xavier Thomas, also remains missing. His girlfriend Christine Delcros is in hospital and her sister shared a post on Facebook asking for help to find them.
"We're en route to London, my sister Christine Delcros and her boyfriend Xavier Thomas have been victims of the #attack #London #londonattack on the #londonbridge. My sister is seriously injured and hospitalised
"I appeal to all those who have news of #Xavier #Thomas who is missing ... We're terribly worried ..." she said.
Another young man, Socaine Drz has been named by family as unaccounted for. His aunty, Hatice Bodur, shared a photo of the young man and asked friends to get in contact if they have seen him, The Sun reports.
"If you see this Socaine please return home. We are worried sick police are looking as well."
On Monday UK Prime Minister Theresa May said the "victims came from a number of nationalities" and it would take some time for authorities to contact the next of kin.
"This was an attack on London and the UK but it was also an attack on the free world," she said.
This undated image provided by the Archibald family shows Christine Archibald. Photo / AP
BROKEN INTO 'A MILLION PIECES'
The family of the Canadian woman named as the first victim have revealed her fiance's heartbreak as he tried to perform CPR on her.
Christine Archibald, 30, was hit by the speeding van on London Bridge. She had been out for a late-night walk to see the sights of London having visited the capital from the Netherlands with her fiance, Tyler Ferguson.
Ferguson's sister said she spoke to her brother on the phone after the attack and urged friends to help support him after his heart had been broken into a "million pieces".
"Last night in London, my baby brother, lost the love of his life on the London Bridge," she said.
"In a split second his entire life was ripped away from him. Hearing his painful sobs on the phone while he's alone trying to deal with this tears me apart."
"I have no words. If you know Tyler, please be there for him now, and later when what happened sinks in, he's going to need us all."
Ferguson's brother Mark told a British Columbia news station that the pair were in London for a week from The Hague where Ferguson works as an accountant. Archibald decided to join him on a work trip.
"She had never been there before so they decided to take a walking tour of London in the night-time," he said.
"He was showing her some sights and walking around and just enjoying the nice night," Mark said before she was tragically struck by the van.
"He tried CPR on her ... First responders showed up right away and they tried to do everything they could for her. She passed in his arms.
