Robert Pattinson thinks Katy Perry is ''so hot''.

The 'Twilight' hunk was spotted flirting with the 'Roar' hitmaker at the after-party for his new movie 'The Rover' in Los Angeles earlier this week, before reportedly telling his friends that he has a crush on the brunette beauty.

A source, who witnessed the duo's cosy behaviour at Whiskey Blue at the W Hotel, told the New York Post newspaper's Page Six column: ''They were heavily flirting. At one point, Robert sauntered to the bar with a pal and was heard saying, 'She's so hot,' nodding in Katy's direction.''

This isn't the first time the pair have sparked romance rumours as they also set tongues wagging at the Coachella Valley Music and Arts Festival in California in April when they spent the whole weekend together.

A source said previously: ''Katy and Rob are the best of friends with a very strong sexual chemistry ... Friends genuinely want to see them get it together properly. They think they bring out the best in each other.''

However, Katy, 29 - who split from her on/off boyfriend John Mayer in February - admitted last year that she see's Robert, 28, more as a brother than a lover.

She said: ''He's my bud, I'm like his big sister. We just hang out.''

Meanwhile, Robert is still in contact with his ex-girlfriend Kristen Stewart, whom he split from last year after it was revealed she'd been having an affair with her 'Snow White and the Huntsman' director Rupert Sanders.