Kristen Stewart, Robert Pattinson Kiss, Nuzzle at Cannes After-Party

Robert Pattinson and Kristen Stewart Dave M. Benett/Getty Images

R-Patz only has eyes for K-Stew–and he doesn't care who knows it.

Robert Pattinson stepped out to support his love of three years, Kristen Stewart, at the afterparty for her new film On The Road, which premiered at the Cannes Film Festival Wednesday night. Once inside the venue, the duo got cozy on a sofa in the VIP section. (Stewart was joined by her costars, and real-life couple, Garrett Hedlund and Kirsten Dunst.)

"They looked really comfortable, sitting closely and chatting," an onlooker tells Us Weekly about the head-over-heels pair. "He was talking to her and not paying attention to anyone else. Every now and then she would laugh and he would smile at her."

The couple took a break to mingle with other partygoers, but it wasn't long before Pattinson and Stewart parked themselves next to one another on the couch again. "They squeezed themselves in to the furthest corner of the sofa possible," the witness shares. "They were talking closely but every now and then Kristen would show him the screen of her phone and he would make a face or laugh. He then took over the chat and she was listening and nodding and then suddenly giggling. It looked like he was telling her jokes."

At one point, the Twilight costars enjoyed their own private karaoke session. "Rob and Kristen were singing along to 'Hit The Road Jack' and got really into it. Both were sitting close, and after the song finished, she nuzzled her head on his shoulder."

Towards the end of the night, Pattinson and Stewart headed out onto the terrace to check out the view–and steal a few smooches. "She put her hand on his chest," the witness tells Us. "They then kissed–several times."

Though Kristen and Rob have been together since 2009, it wasn't until last October that Stewart finally confirmed their relationship–by accident.

During a chat with GQ, the actress commented that, while filming Snow White and The Huntsman in England, she hoped to explore the country more "because my boyfriend is English."

More recently, she played coy about engagement rumors in her June interview with Elle.

"Everyone wants to know. Everyone knows already," Stewart told the mag. "It's ridiculous."

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