"There were five horses. They have all been recovered. Three of them are fine, two of them are unfortunately in a relatively serious condition and obviously we will be monitoring that condition," defence minister James Cartlidge told Sky News.

The names of the injured horses are Vida and Quaker, he added.

Seven horses and six soldiers from the Household Cavalry were on an extended exercise in Belgravia, near the regiment's barracks off Hyde Park, when the chaos erupted on Wednesday morning.

Four service personnel were thrown from their horses, with five of the animals getting loose, reportedly after they were spooked by concrete being moved by builders hitting the ground.

Two horses then ran along busy roads, dodging buses, taxis and other traffic.

Three of the unseated soldiers were taken to hospital where they were being assessed but none was in a life-threatening condition.

A number of prestigious army cavalry regiments have stables in the British capital and horses are a regular sight around government buildings on Whitehall, Buckingham Palace, The Mall and in nearby Hyde Park.

Cartlidge stressed that Wednesday's events were "extremely unlikely" to be repeated.

"You are probably aware that the army has horses out on exercise in central London every day of the week. It is about 150 horses on average exercising every day," he told LBC radio.

"So this is extremely unlikely, this scenario."

London Ambulance Service said it was called at 8:25 am (0725 GMT) to reports of a person being thrown from a horse on Buckingham Palace Road.

Two of the horses were recaptured by the City of London Police, which polices the Square Mile financial district.

Officers contained two animals while "an army horse box had collected the horses and transported them to veterinary care".

The driver of a Mercedes car told LBC radio he had been waiting outside a hotel in Buckingham Palace Road when he felt something smash into his car.

He said he saw three or four horses near the vehicle, and that an army rider had been thrown off and injured.

One horse crashed into a parked double-decker tour bus, smashing the windscreen.