She is the latest celebrity to endure a high-profile relationship breakup.

But Naomi Watts is back at work - with a beaming smile on her face - days after announcing she and boyfriend Liev Schreiber had split after 11 years together.

The 48-year-old mother of two celebrated her birthday in New York on the set of her upcoming Netflix series, Gypsy.

She shared a cheeky snap of her unusual birthday cake on Instagram, taken by Fifty Shades of Grey director Sam Taylor-Johnson, who is directing Watts in Gypsy.

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She stars alongside Billy Crudup in the 10-episode Netflix series, described as a psychological thriller.

Schreiber was also photographed in the Big Apple this week, on a push bike with Alexander and Samuel, the sons he shares with Watts.

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In a joint statement this week, Watts and Ray Donovan actor Schreiber announced their separation.

"Over the past few months we've come to the conclusion that the best way forward for us as a family is to separate as a couple," the statement said.

Naomi Watts and Liev Schreiber announced their separation this week. Photo / AP
Naomi Watts and Liev Schreiber announced their separation this week. Photo / AP

"It is with great love, respect, and friendship in our hearts that we look forward to raising our children together and exploring this new phase of our relationship."

"While we appreciate your curiosity and support, we ask the press to be mindful of our children and respect their right to privacy."