Rihanna Unveils New Track 'Birthday Cake' Featuring Chris Brown - Listen

Rihanna and Chris Brown have unveiled their new collaboration 'Birthday Cake' – you can listen to it below.

The pair, who dated until Brown assaulted the singer in 2009, have both posted the new remixes online.

Brown wrote on his Facebook: "The pub and excitement of this industry /society is only a surface! Really want us as a human race to unite! Bigger than music! (sic)"

Rihanna wrote to Brown on Twitter: "'Turn up the music' remix," then added: "It's a download OVERLOAD!!! Working on more links for u guys, so err body could have some #CAKE.

The collaboration has now fuelled recent rumours that they are back together.

The singer and her ex Chris Brown spent Valentine's night together as they celebrated her birthday in LA alongside friends.

Katy Perry, Bruno Mars and Kelly Rowland all attended the bash in Beverly Hills on Tuesday.

A source told the Daily Mirror: 'Rihanna and Katy had everyone going crazy. By the end of the night they started a cake fight and were dancing together while Bruno and Chris looked on open-mouthed, cheering.''

One party guest tweeted: ''If Cupid was here he would be very happy everyone @Rihanna bday party was coupled up.'

She added: 'All I can say, CB was invited and she [Rihanna] was acting like the happiest girl on her birthday and probably got what she asked for.'