A heartbreaking video of a man singing a Beatles song to his dying newborn baby, after the mother died, has gone viral online.

Chris Picco took a guitar into the neo-natal ward to sing Blackbird to his son Lennon, born prematurely by emergency Caesarian section last weekend.

The boy was born at 24 weeks on November 8 after his mother Ashley suddenly died on the same day.

The infant survived three days in the neo-natal ward at Loma Linda University Hospital outside Los Angeles and died on November 11.

A video of the baby’s father playing the song by his incubator had been watched by more than half a million times on Thursday with tens of thousands more views every few minutes.

“Our dear Ashley’s life was tragically, devastatingly cut short this past weekend. Her dear baby flickered briefly for a few days after,” said a statement on a memorial website.

The memorial fundraising site was established to help Mr Picco pay for “substantial medical costs” and had raised more than $90,000.

In statements to the page Mr Picco had updated progress on his tiny son’s life saying he was “so thankful for the four unforgettable days” he was able to spend with him.

“My little fighter, Lennon James Picco went to sleep in his daddy’s arms late last night. He was surrounded by family, friends, and the best doctors, nurses and hospital staff in the world. He was dressed in an outfit that Ashley bought for him, with little guitars on it, and wrapped in a blanket made by a dear friend,” he said in a post on the site.

“His mommy would have been so beyond joy to see him and to hold him, touch him, bathe him, sing to him — as I have had the privilege of doing. I have been so blessed and honored to love him before he was formed, to cherish him while mommy carried him, meet him face to precious face, and hold his perfect little body while we said ‘goodbye for now.’ There are no words.”

Ashley and Chris Picco. Photo: Ashley Picco Memorial Fund