'The Hunger Games' star Liam - who split from fiancé Miley Cyrus last year - was in the Corner Tavern in Atlanta, US, on Friday (07.02.14) with 'The Vampire Diaries' actress and an eyewitness says they even ended their night with a "sensual" kiss.
Jahti Anderson told Celebuzz.com: "They stayed around two to three hours and Nina left before Liam, and as she was leaving they gave each other a good night kiss... [and] she ran off into a car service with her friend.
"The kisses were on the lips publicly outside of the bar ... and it was three sensual kisses on the lips. They stuck together pretty much the whole time, but I think Nina got sick of pictures [with fans] because Liam was the highlight, so to speak."
While they were with other friends and happily posed for pictures separately, Jahti claims they acted like they were on a date.
She added: "They were there together and were with a couple other friends.
"They were having a great time. They were definitely acting couple-y. They were drinking beers and mostly standing and talking near the bar."
Liam, 24, is in Atlanta filming 'The Hunger Games: Mockingjay', while Nina, 25, is working on the latest episodes of 'The Vampire Diaries' in the same city.
Liam dated Miley for three years before getting engaged in June 2012, but called it off last September. Miley, now 21, later said she "wouldn't change" having been engaged, but thought she was too young to get married at the time.
Nina previously dated her 'The Vampire Diaries' co-star Ian Somerhalder for three years, but they split in May 2013.