The couple spurred rumours that they will tie the knot this weekend with a private party for friends at Cala Masciola beach on the Adriatic Sea, according to Us Weekly.
© Rex Features / Billy Farrell Agency
Andy Samberg and music manager Johnny Wright were both photographed at the event, where guests enjoyed dinner and music.
The night was apparently capped by a ten-minute firework display in celebration of Timberlake and Biel's imminent nuptials.
It was previously reported that Timberlake will likely perform an *NSYNC dance medley during the wedding party.
Biel and Timberlake got engaged earlier in 2012 after dating on-and-off for several years.
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