This is the chilling moment a woman dressed as a nurse walked away with a baby boy taken from his mother and stuffed in a rucksack in a hospital maternity unit.

The footage shows the woman dressed in scrubs walking down a hospital corridor with the infant in her arms at the San Juan de Dios hospital in San Miguel, El Salvador on December 30.

Moments earlier she had told the baby's trusting mum that she was taking him away for feeding.

Shockingly, as the security footage continues, the fake nurse stops and horrifyingly stuffs the newborn into a rucksack.

One patient walks by but takes no notice before the baby-snatcher slings the bag over her shoulder and strolls off.

The mum reportedly only realised what had happened when a real nurse on baby feeding duties later turned up to collect her son.

It later emerged that the baby had been retrieved after two suspects tried to pose as his biological parents and were arrested. The woman seen in the video has not yet been arrested.

Relatives told local media he had gone through a high-risk birth and needed medical supervision to make sure he had been stabilised before he could be discharged.

A National Civil Police spokesman said: 'This is the video of the moment in which the woman pretending to be a nurse takes the baby in a backpack to go unnoticed.

'We are investigating and we will bring her to justice so that she is punished to the fullest extent of the law.'

The investigation is ongoing. Neither the suspects nor the victims were named.