The former couple have fuelled reports of an apparent reunion in recent months, having collaborated on songs and appearing to share a kiss at this year's VMAs.
They have since been spotted together at several public and private events, most recently at the after-party for Chris Brown's concert in Germany.
According to WENN, after wrapping up her '777' tour Rihanna flew to Berlin on Thursday (November 22) to watch Brown perform at the O2 World Berlin concert venue.
She was later seen with him at the Adagio Nightclub, where they were photographed leaving the party in the same car.
The 'Diamonds' singer seemed to make an allusion to Brown in a series of Twitter posts when she wrote: "All alone in my big ole jet!!! See u soon lover… Happy Thanksgiving everyone… #Berlin #Carpe Diem."
Carpe Diem is the name of Brown's tour.
Brown's tour has run into some recent trouble after allegations that he illegally backed out of a scheduled show in Guyana next month.