Justin Bieber and Selena Gomez were all over each other at a friend's birthday party.

The 'Baby' hitmaker rented out the Lucky Strike bowling alley in Los Angeles on Sunday night (14.09.14) for their pal Ryan Butler's intimate celebration, and couldn't keep his hands off the 'Come & Get It' singer at the party.

A source told E! News: ''Justin rented out Lucky Strike's Luxe room for the celebration. Additionally, he was seen kissing and flirting with his on-and-off again girlfriend, Selena Gomez.''

The insider added: ''The group, of about 12 people in all, enjoyed some of Lucky Strike's Esteban's Nacho's Grande, Cheeseburgers and wings. Specifically, Justin was seen eating the Mac & Cheese bites.''

Ryan's girlfriend posted a photograph of Selena, 22, gazing at Justin, 20, on Instagram from the party.

The Canadian star confirmed during a deposition last week that he has reunited with his on-again, off-again girlfriend, whom he first started dating in 2010.

A source close to Selena previously said: ''There will forever be an emotional connection for them, but they don't have a title to their relationship.''