Pop star Christina Aguilera treated freezing fans in New York City to free coffee as she made an unexpected visit to a local Starbucks on Monday (16Feb15).

The Beautiful hitmaker paid a visit to the tourist-heavy Rockefeller Center concourse, and stopped by the popular coffee shop much to other customers' surprise.

A source tells E! News, "There were only about 10 people in the store at first, but when people started to realise who she was more and more (people) came in. She took a lot of time to take pictures with the customers."

Aguilera also took to Twitter.com, posting a photo of herself autographing a paper cup, and added the caption, "Coffee on me for the next hour! Head to 30 Rock (30 Rockefeller Plaza)! Xo Xtina."