Singer Katy Perry arrives at the 54th annual Grammy Awards in Los Angeles, California February 12, 2012.[Photo/Agencies]

Katy Perry has been partying until the early hours as she tries to get over her split from Russell Brand.

The 'Firework' singer split from the British comedian in December after 14 months of marriage, and stayed out until three am this morning (23.02.12) partying with a group of her friends - including guys - in Hollywood.

A source told LifeandStylemag.com: "Katy was partying with a bunch of pals at the Spare Room at the Roosevelt Hotel in Los Angeles.

"She came in around 1.30am. She was wearing a grey sweatshirt and sweatpants with blue high pumps.

"She was also with a bunch of male friends, and they played numerous games of bowling.

"They were drinking mixed vodka drinks and having a blast."

Although the Spare Room usually shuts at 2am, it stayed open especially for Katy and her pals.

The source added: "It was obvious that she liked being out and having a fun, carefree time, without crowds of people around her.

"She was all laughs and smiles with her friends.

"Security left at 2.15am, but Katy stayed behind with her pals and continued the party."

Meanwhile Russell - who is also in Los Angeles - is rumoured to have recently spent a night with model and artist Oriela Medellin Amieiro, and sources have suggested he is already going back to the womanising ways he was famous for before he met Katy.

A source told Us Weekly magazine the 'Arthur' star is "definitely playing the field. And he never mentions Katy."