The 34-year-old actor - who split from wife Scarlett Johansson last December - is said to have been dating the 35-year-old actress "for months" but the pair have been deliberately keeping the romance under wraps.

A source told Us Weekly magazine: "They have been dating - for months! They`re exclusive, and it`s very hush-hush."

The pair have not yet been photographed together, but the magazine reports that witnesses saw the `Green Lantern` actor`s motorcycle parked outside Charlize`s house all morning one day last month, before Ryan eventually emerged from the property at 3pm and she left just minutes later.

Insiders believe the pair make a good couple because of their similar attitudes to work.

One source said: "They`re both career-focused but not in a crazy way."

However, Charlize - who ended her nine-year relationship with Stuart Townsend last year - is not planning to be seen in public with Ryan any time soon.

The source said: "She won`t go to an event with him. That`s not her style."

Meanwhile, Ryan recently found the time to have dinner with 26-year-old Scarlett at Little Dom`s in Los Angeles.
sections: Celebrities