Scarlett Johansson flashed a huge diamond ring at the Metropolitan Museum of Art's Costume Institute Gala, hours after confirming her engagement to Ryan Reynolds.

The 23-year-old actress unveiled the diamond ring while walking the red carpet, flanked by designers Domenico Dolce and Stefano Gabbana.

Scarlett Johansson's publicist, Marcel Pariseau, said earlier in the day that Johansson and Reynolds were engaged and had not yet set a wedding date.

The couple reportedly had been dating for more than a year. Scarlett Johansson joked about her rumoured engagement showing her affection for presidential hopeful Barack Obama: "My heart belongs to Barack, and that is who I am currently, finally, engaged to. Yes."