Bieber, 20, and Gomez, 21, had sparked rumours that they had rekindled their romance earlier this month after the duo were seen together on several occasions, reported Hollywood Life.
"The ring was a gift from Justin, it's not an engagement ring, but they are back on and very serious. Her family is extremely worried that she'll do something crazy like elope with him," a source said.
"Selena is totally wrapped back up in Justin, it's the same pattern happening all over again," the source added.
Recently Bieber had posted a picture of Gomez on Instagram which was captioned as "The most elegant princess in the world.