Wearing wide-grins and gushing praise for one another, but ducking questions about a possible relationship, Mr and Mrs Smith co-stars Brad Pitt and Angelina Jolie briefly visited Mexico's capital for the premiere of their film.

The pair flew into an airport 55 kilometres West of Mexico City and a fleet of black and white sport utility vehicles drove them for more than an hour to a sprawling, upscale shopping centre in the Santa Fe district, last night.

Several hundred screaming fans filled bleacher seats underneath a tent set up outside the shopping centre's movie theatre complex and hundreds more waited for hours to catch a glimpse of the pair in the parking lot.

"I'm so excited, he was right in front of me," 16-year-old Alejandra Najera Gomez said of Pitt.

Fanning herself with her hands, she said she and a friend had waited three hours, then added: "he's so cuuuuuuute!"

Sporting stubble, short hair and a low-key short-sleeve shirt, Pitt posed for photographers, signed autographs and called Jolie "a firecracker."

"She's dear to my heart," he said. "You never know what she's going to say."

When asked about a shortage of steamy love scenes in the movie, Pitt smiled and said, "it's pg-13. What are you going to do?"

The two reportedly became romantically involved during filming of Mr and Mrs Smith which opens tomorrow and is about husband-and-wife assassins who are clueless about each other's occupation until each is hired to kill the other.