Rumours are circulating that Justin Timberlake and Cameron Diaz may have split, and that the pop star has hooked up with actress Scarlett Johansson.

eTalk reported Friday that Timberlake went solo to the premier of "Alpha Dog," in which he has a significant role, and was later seen with Johansson at the after-party.

According to various celebrity gossip sites, Timberlake has been hanging out with Johansson since late December, when the two filmed his new music video for "What Goes Around..."

Johansson recently split from her boyfriend Josh Hartnett, while Timberlake and Diaz haven't been spotted together for weeks, when he hosted Saturday Night Live.

Rumours about a possible Timberlake-Johansson relationship flared Wednesday, when the two were seen chatting away at the "Alpha Dog" party.

The same night, celebutante Paris Hilton apparently made a play for Timberlake. But according to eTalk, one witness said he looked "bored."