Scotland Yard said that Londoners should not be “alarmed” by the increased police presence but urged people to report anything that “doesn’t feel right”.
The appeal comes in the wake of an increase in Britain’s official terror threat level, which was upped from “substantial” to “severe”.
The move to deploy extra police onto the streets of London has been done so to protect high streets, transport hubs and other potentially vulnerable locations in response to heightened fears of a terror attack following the Islamist killings in Vienna and France.
That means an attack is deemed to be “highly likely” in a move that was prompted by Sunday night’s rampage in Vienna in which four people were killed and several more critically injured by Islamic State supporter Kujtim Fejzulai.
Fejzulai was shot dead by police soon after starting his attack, in which he used an automatic rifle to fire at people enjoying a night out in a district of central Vienna lined with bars and cafes. He was also carrying a pistol and a machete and wearing a fake suicide belt.
A total of 14 people have been arrested in Austria in connection with the attack during raids in Vienna and another two men, aged 18 and 24, have also been arrested in the Swiss city of Winterthur near Zurich.