A man offered up a young boy for sex to a tourist in Central Park last night, police say.

The tourist, 50, called 911 after a man, who appeared to be the boy's father, asked if he would like to have sex with the child for $300.

The Californian tourist declined and followed the pair - aged around 35 and 11 - for a short time as he called the cops.

By the time police arrived, the man and boy had gone.

The incident took place at around 11.50pm on Thursday.

Police were last night searching near Central Park's Bow Bridge on West 74th Street on the Upper West Side of Manhattan, ABC 7 reported.

The NYPD said it would study surveillance footage in the park as officers hunt down the man.

The tourist said the man was white, had dark hair, was clean shaven and was wearing a black coat with a furry hood and blue jeans.

The young boy was also white and was wearing an orange or red jacket.

Anyone with information is urged to call the NYPD.