The threats against the Duchess of Cambridge have been made on messaging service Telegram and encourage fanatics to tamper with her food.
In one image, the 37-year-old is shown with a red X on a shopping trolley with the caption: 'We know what she eats – poison it!'
Additional threats have been made towards her son Prince George and information about where she goes shopping.
The messages are being taken 'very seriously', as reported by the Daily Star Sunday.
A source told the newspaper: 'Intelligence agents believe the threats made against Kate are not idle and are linked to messages sent by Husnain Rashid.
'It's a disgusting plot as it involves Kate's young children, and hits out at her attempt to live a normal life like any mother wants to.'
Husnain Rashid was jailed for life with a minimum of 25 years for calling on ISIS supporters to attack Prince George.
The 32-year-old used a Telegram chat group to urge supporters to target the heir to the throne.
Rashid, from Lancashire, posted a photograph of the prince at his school super-imposed with silhouettes of two masked jihad fighters.
During his May 2018 trial, prosecutor Annabel Darlow told the court Rashid messaged the Telegram group with a picture of the young prince, saying: 'Even the royal family will not be left alone.'
He added: 'School starts early.'
Rashid also posted suggestions of which British football stadiums terrorists could strike following the deadly attack outside Besiktas’s ground in Turkey.
And in addition to that he plotted to inject ice cream with poison.
Kensington Palace has been been approached for comment.