The runaway carriage hit two cars. The photo was uploaded to Twitter by @pcsegal.

The runaway carriage hit two cars. The photo was uploaded to Twitter by @pcsegal.

An Australian couple have been injured after the horse pulling their carriage through New York's Central Park tore away and caused chaos in midtown Manhattan, US reports say.

The two tourists, from Queensland and aged 32, were on an afternoon ride when the horse reportedly bolted in fear, losing its driver and then breaking off from the red and white carriage causing it to tip, leaving the pair sprawled on the street.

The brown and white six-year-old horse, named Oreo, then ran several blocks through busy afternoon New York traffic and collided with two parked cars before he was stopped by a police officer and a passer-by.

The horse was shot with a tranquilizer dart. Photo posted by @StrongFitMom on Twitter.

The horse was shot with a tranquilizer dart. Photo posted by @StrongFitMom on Twitter.

Oreo was shot with a tranquiliser dart but later stood up and was taken away by New York Police Department's mounted officer division.

The couple were taken to St Luke's Hospital in a stable condition with minor injuries, a New York Police Department spokeswoman said. Oreo was also expected to be fine.

Witnesses have given different versions of what caused the horse to bolt at 4.20pm (Thursday, New York time). Some said it became spooked by the loud horn of a truck while others have told US media outlets that the horse simply became spooked when its driver tried to merge with heavy traffic.

"It was a little scary seeing a horse running down 9th Avenue," a witness, Gaelle Paul, told the New York Daily News.

Horse-drawn carriages in Central Park, while popular with tourists, have drawn criticism from animal welfare groups who want them outlawed.

Two years ago, a horse name Charlie dropped dead while working as a carriage horse, while in 2007, a horse named Smoothie was killed after it crashed into a tree after being startled by a loud noise.