The lovebirds Justin Bieber and Selena Gomez are in news again and this time with their engagement news. However, both the singer denied the report.

Bieber Thursday celebrated his 18th birthday, and his girlfriend Gomez posted a message on his Twitter account: Happy birthday to my best friend in the world world!!!.

She wrote: Have a great birthday baby!

The couple might have celebrated some time together, but Gomez took to Twitter to let all their fans to know how much she loves Bieber.

The slideshow here gives a peep into the growing bond of love between the young singers.

Justin Bieber and Selena Gomez
Justin Bieber, left, and Selena Gomez arrive at the MTV Video Music Awards on Sunday, Sept. 12, 2010 in Los Angeles. Reuters
Justin Bieber and Selena Gomez
Selena Gomez, left, hugs Justin Bieber after he won the best male video award for "U Smile" at the MTV Video Music Awards on Sunday, Aug. 28, 2011, in Los Angeles. Reuters
Justin Bieber and Selena Gomez
Selena Gomez, left, and Justin Bieber arrive at the 39th Annual American Music Awards on Sunday, Nov. 20, 2011 in Los Angeles Reuters
Justin Bieber Buys Ashton Kutchers 10.8M Mansion For 18th Birthday
Pop star Justin Bieber is reportedly buying the $10.8 million home Ashton Kutcher has been renting out in the Hollywood Hills, an 18th birthday present for him and his girlfriend Selena Gomez. Check out the five-bedroom, eight-bathroom mansion here, and find out what else the pop star got for his birthday. Reuters
Justin Bieber and Selena Gomez
Justin Bieber accepts the award for "Ur Fav Artist" for his song "Somebody to Love" from host Selena Gomez during the MuchMusic Video Awards in Toronto, June 19, 2011 Reuters
Justin Bieber and Selena Gomez
Justin Bieber (L) accepts the International Video of the Year by a Canadian award for "Somebody to Love" as host Selena Gomez looks on during the MuchMusic Video Awards in Toronto, June 19, 2011 Reuters
Justin Bieber and Selena Gomez
Singer Justin Bieber speaks to singer Selena Gomez as he is announced as the recipient of the Choice Music: Male Artist Award at the 2011 Teen Choice Awards at the Gibson amphitheater in Universal City, California August 7, 2011. Reuters
Justin Bieber and Selena Gomez
Singer Justin Bieber, holding a snake in his hand, kisses Selena Gomez as they arrive at the 2011 MTV Video Music Awards in Los Angeles, August 28, 2011. Reuters
Justin Bieber and Selena Gomez
Singer Justin Bieber kisses his girlfriend, singer Selena Gomez, as they arrive at the 2011 American Music Awards in Los Angeles November 20, 2011. Reuters
Justin Bieber and Selena Gomez
Singer Justin Bieber carries the train of Selena Gomez's dress as they arrive at the 2011 American Music Awards in Los Angeles November 20, 2011. Twitter fans of the two singers on Saturday, began the trending topic "Stop Selena Hate," asking that others respect the singers' relationship. Reuters
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