London, July 18 - Pop singer Rihanna was spotted recently walking past her London hotel with rapper and producer Pharrell Williams.

Mirror.co.uk reports that witnesses said there seems to be 'obvious chemistry' between the two. Rihanna recently split from singer Chris Brown after he allegedly assaulted her.

A source said: 'It's no secret that Rihanna and Pharrell have chemistry. And not just in the studio -- they seem mesmerised by each other. But Chris will be gutted to learn he could have lost Rihanna to one of the sexiest men in music. Rihanna and Pharrell talk on the phone all the time and whenever she can get a break in her schedule she'll go and support him at a gig.'

Williams and Brown have been friends for a while and even collaborated professionally.