A 19-year-old tourist suffered a severe injury to his left foot in an explosion in Central Park, said a spokesman for the New York Police Department, which was investigating the cause of the incident.

The teen was in the park with two friends, who had also travelled to New York, when the blast occurred just before 11 am near East 61st Street and East Drive, the NYPD spokesman said.

"He stepped on a rock or some object and there was an explosion that followed," the spokesman said.

He was hospitalised in critical but stable condition.

Police said they were investigating whether the blast, occurring the day before the city's Fourth of July pyrotechnics show, involved a firework or some other kind of explosive.

No further information was immediately available.

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