It has also been reported that supporters of Isis made chilling threats overnight on Twitter, from a now-disabled account, stating that London could be next.
One 25-year-old Aucklander living in London, who asked not to be named, said in the wake of the Paris deaths he realised an attack could occur anywhere.
"I was in Trafalgar Square today and I looked around and I thought 'Wow'. I felt quite vulnerable in a public place. I was well aware that something could go on there," he said.
"It feels very close to home since we're just one train away from Paris. It's quite scary."
Another Kiwi, who works in a London fabric store, said she had noticed the difference between her attitude and her colleagues' even before the attacks.
"Some of the people I work with, they're from England, and it's a consistent thought of theirs. It's not just that they're thinking it now [after the attacks], they've brought it up a couple of times," she said.
"It's just a thing they consider much more than us back home. It's always a threat.
"For us here it's a bigger thing. It's something to think about."
She was meant to be going to France for Christmas but would have to think about the situation closer to the time, she said.
The group had been to key "tourist spots" in London today including Buckingham Palace, Hyde Park and Big Ben but said there was no noticeable change in atmosphere in the city.
One of the Kiwis said it seemed like most Londoners were trying to keep things normal.
"Everyone's trying not to think about it," she said.
"If something happened in London itself that would be different."
London was last hit by a terror attack in 2005, when a series of co-ordinated suicide bomb attacks killed 52 people and injured a further 700 using underground trains during morning rush hour.
