The Biebs and Hailey were spotted hanging out down in M-I-A on Sunday ... first hitting up a church conference before chowin' down at the ritzy Casa Tua, and then hitting up LIV Nightclub at Fontainebleau.
Our sources say Justin and Hailey walked in together around 1 AM ... where they hung out on a VIP balcony, held hands and danced together. They were definitely not trying to keep things on the DL ... showing plenty of PDA for all to see.
Justin goofed around a bit too ... busting out the Floss dance as the crowd cheered him on.
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We're told Hailey and Justin left the club around 3 AM holding hands.