'Avengers: Infinity War': Paul Bettany, Elizabeth Olsen kiss on set

April 20 (UPI) -- Avengers: Infinity War stars Paul Bettany and Elizabeth Olsen were spotted kissing on set this week.

The 45-year-old British actor and 28-year-old American actress shared a smooch as Vision and Scarlet Witch while filming the Avengers: Age of Ultron sequel Tuesday in Edinburgh, Scotland, according to E! News.

Sources said Bettany and Olsen filmed the same scene "eight or nine times." The scene begins with Vision opening the window curtains with his abilities, and ends with him and Scarlet Witch getting "very close and finally" kissing.

Romantic tension between Vision and Scarlet Witch began in Avengers: Age of Ultron (2015) and continued in Captain America: Civil War (2016). Olsen discussed the relationship with Red Carpet News TV in May.

"I think it's something that fans have wanted, but we're just trying to root it into something that's, like, more pure, of a friend and a companion," she said.

"[Scarlet Witch is] made from his stone, basically, so we have that in common," the star added of Vision's Mind Stone, which unlocked her character's powers. "To use that as a thread that roots our relationship is really important and grounding in a way."

Avengers: Infinity War will see Vision, Scarlet Witch, Iron Man (Robert Downey, Jr.), Captain America (Chris Evans), Black Widow (Scarlett Johansson) and Thor (Chris Hemsworth) take on Thanos (Josh Brolin). The movie opens May 4, 2018.