Police forensics team examine a car in Parliament Square on March 22, 2017 in London, England.

A terrorist attack involving a vehicle mowing down pedestrians near Britain's Parliament that killed four on Wednesday is the latest case in what experts say is a growing threat of low-tech terrorism in the West — and bore resemblance to an attack four years ago on a British soldier.

At least 40 more people were injured in the latest incident when the 4x4 vehicle slammed into pedestrians on the Westminster Bridge, before crashing into a railing near Parliament. A police officer was then stabbed near Britain's House of Commons, officials said.