The US Office actress Mindy Kaling has surprised fans by revealing that she has given birth to a second child.

The comedy writer and director said she welcomed a son, named Spencer, on September 3. She had not previously revealed she was pregnant.

41-year-old Kaling shared the news during an appearance on US chat show The Late Show With Stephen Colbert and said: "I'm telling it for the first time, it feels strange but I gave birth to a baby boy on September 3."

She added: "This is news to a lot of people, it's true."

Kaling already has a two-year-old daughter named Katherine. Kaling has never shared a picture of her daughter's face or the identity of her biological father, saying it was important to maintain some privacy.

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She has revealed that her former US Office co-star BJ Novak is Katherine's godfather.

"The truth is that BJ is so much more like family now than a platonic friend," Kaling told Good Housekeeping. "He's the godfather to my daughter, he comes over like once a week. Sometimes he'll come over just to hang out with her."

Last year Kaling wrote and starred in the comedy Late Night, appearing alongside Emma Thompson.

Her Netflix coming-of-age comedy-drama Never Have I Ever arrived in May to critical acclaim.