Katy Perry and Orlando Bloom getting serious?

Orlando Bloom and Katy Perry flirted up a storm at a Golden Globe after party. Photo / Getty

Katy Perry and Orlando Bloom are continuing to keep fans guessing about their rumoured romance by attending a birthday party at Robert Downey Jr's home over the weekend.

The Lord of the Rings star and the pop singer first hit headlines last month when they partied together after the 2016 Golden Globes.

They were then spotted attending actor James Lecesne's play, The Absolute Brightness of Leonard Pelkey and were pictured getting close at a Hollywood dinner party last Wednesday.

Now it appears the relationship is getting serious after Perry joined Bloom on Saturday to take his son, Flynn, to a birthday bash for Downey, Jr's boy, Exton at the actor's Malibu mansion.

"Katy was entertaining Flynn so he wouldn't get bored," a source tells UsMagazine.com.

"It was a long drive and she was talking to him and making him laugh. They were laughing, playing music and joking around with Flynn (at the party)," another insider adds to People.com.

"They stayed at the party for hours. Katy looked very comfortable at the kids' party. She seemed very happy to spend the day with Orlando."

Orlando and Katy have yet to comment on the status of their relationship, but sources previously told People.com the two enjoyed some "aggressive flirting" at Harvey Weinstein's post-Globes bash, saying, "Katy and Orlando were standing in the back of the party drinking Moet (champagne) and were aggressively flirting before leaving together. She was very flirty and laid on the charm."

Bloom was previously married to Australian model Miranda Kerr from 2010 to 2013 and they welcomed son Flynn in 2011.

Perry divorced comedian Russell Brand in 2012 after two years of marriage.

- AAP