The Baby singer pitched his new album, Purpose, against the boyband's Made in the A.M., and he came out on top following a tense chart battle.

After hearing news that he had clinched the top spot, Justin headed to L.A.'s Hyde Sunset Kitchen + Cocktails venue with a group of friends to celebrate, according to the New York Post.

Editors of the publication report Justin thrilled other guests at the venue by taking over the microphone and singing a number of his hit tracks.

"Justin was in such a good mood, he jumped on the mike (sic) to perform a number of songs," an onlooker tells the publication.

The singer scored a huge hit with Purpose, the follow-up to 2012's Believe, setting a new record for the biggest U.S. sales week of 2015 and landing his sixth number one on the American charts.

Purpose shifted 649,000 copies in the U.S., leaving One Direction in second place on the Billboard 200 chart with 459,000, and it marks the highest-selling release of Justin's career so far.

However, One Direction still enjoyed a triumphant weekend (21-22Nov15) as they scooped a top prize at the American Music Awards.

The boyband was named Artist of the Year for the second time in a row at the ceremony in Los Angeles on Sunday night (22Nov15), and they also picked up the prize for Favorite Band, Duo Or Group - Pop/Rock.

"Wow, this is absolutely incredible to receive this award now two years in a row," bandmember Louis Tomlinson said during the band's acceptance speech. "Thank you so much. This is a testament of how incredible our fans are. You've been great to us this year, so thank you."

Justin picked up one prize at the gala, scoring Collaboration of the Year for Where Are U Now, his track with Skrillex and Diplo.