Dave Bedrosian / Future Image / WENN 1 / 9
Dave Bedrosian / Future Image / WENN 1 / 9

It's been a busy week for Justin Bieber.

Two new reports are claiming that the Biebs is not only hooking up with a Kardashian, but that just days earlier, he indulged in a threesome while partying after a London performance.

On Dec. 12, Gossip Cop revealed that the 21-year-old pop star has been "casually hooking up" with single mom Kourtney Kardashian, 36, a source told the website.

According to Gossip Cop's source, the romance is not serious and only occurs occasionally because for the odd couple, "it's just fun."

On Dec. 11, Kourtney -- who split from Scott Disick this summer amid reports of his wild partying and a cheating scandal -- was spotted hanging out with the Biebs at Los Angeles nightclub The Nice Guy and again at karaoke club Blind Dragon before she headed to the Montage Beverly Hills hotel, where Justin often stays, Gossip Cop reports. She was photographed leaving the hotel at 4 a.m.

The Friday-night encounter follows previous outings, including one in October when the pair had dinner at The Nice Guy and hit Universal Studios' Halloween Horror Nights event together.

Then on Dec. 13, news emerged from U.K. newspaper The Sun claiming that Justin had enjoyed a wild romp a few days earlier with model Laura Carter.

Laura, 30, told The Sun that she had "amazing" sex with the pop star after he saw her on a nightclub dance floor after his Dec. 6 Jingle Bell Ball performance at the O2 Arena and invited her back to his suite at London's Rosewood Hotel.

There, she tells the Sun, she had to put her phone in a bucket before joining Justin and a group of four men and 10 women at a party where "Justin was showing off his dance moves."

A game of Truth or Dare ensued, she explained, and she ended up in Justin's bedroom with a second woman who was clad in lingerie. "We got on to the bed and all started fooling around together," Laura said.

She also told the newspaper that naked pictures of Justin that leaked online in October "did not do him justice."