Family desperate to find missing Aussie woman last seen on London Bridge during terror attack

There are serious concerns held for a missing Queensland woman who became separated from her friends during the London terror attacks.

Sara Zelenak, 21, was on London Bridge when a van hit a number of pedestrians just after 10pm on Saturday.

Despite usually being in regularly contact with her family back in Australia, they haven't heard from her since.

Sara's mother, Julie Wallace, is now on her way to London to search for her daughter, who had been given the night off from her nannying job at the last minute to spend time with friends.

Prime Minister Malcolm Turnbull confirmed an Australian ‘named in the press today’ was one of two citizens authorities had ‘real concerns’ for, according to the Herald Sun.

'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.

Sara's distressed friend Pri Goncalves confirmed that they became separated when the attacks started.

'Sara was with me when people started running and shouting but at that very moment we got separated,' she told Fairfax.

'So I started calling her, but she never picked up the phone.'