London, July 16 (IANS) The sixth instalment of Harry Potter has smashed US box office records by raking in a whopping $22.2 million in less than 24 hours and it is said to be the best midnight opening of all times.

The booking for "Harry Potter and the Half-Blood Prince" opened Wednesday.

Starring Daniel Radcliffe, Rupert Grint and Emma Watson, the film hit the screens worldwide Thursday. It has topped "The Dark Knight" midnight earnings of $18 million when it was released last summer and the $17 million earnings grossed by "Star Wars: Episode III - Revenge of the Sith" in 2005, reports femalefirst.co.uk.

The latest Harry Potter movie has even cast its spell over a record number of Potter fans - the new film drew more devotees in its first few hours on show than 2007s "Harry Potter and the Order of the Phoenix", which took $12 million on its first day of release.

"...Half-Blood Prince" will topple the "Transformers" action sequel as the world's most popular film of the year, if opening figures are anything to go by - "Revenge of the Fallen" 12-day total stood at $600 million, say experts.