Kanye West's kids pranked him by pretending their mother Kim Kardashian West was dead.

The 'Stronger' rapper was left unimpressed by five-year-old North's ''ridiculous'' April Fool's joke, which saw her enlist the help of her three-year-old brother Saint to cover the 'Keeping Up With the Kardashians' star in ketchup like a ''bad scary movie''.

Kim - who insisted she didn't realise what her daughter was planning - said: ''[North and Saint] are starting to get closer now that she can include him in her jokes.

''She roped him into an April Fool's prank yesterday that was ridiculous. She took ketchup into my bathroom, and she begged me to let her spread it on me, and on the bathroom, as if it was like a bad scary movie.

''Then she asked me to lie down. I thought she was just playing, maybe that she was going to say I was hurt. No.

''She taught Saint how to fake-cry - she showed him how to do it! - and then she told him to scream 'Mommy's dead!'

''Kanye ran upstairs and he was like, 'Kids, this is not funny. This is not a good prank.' ''

While the 38-year-old beauty agreed with her husband, she was also ''impressed'' by the team work employed by the pair, who also have a 14-month-old sister, Chicago.

She added in an interview with America's Elle magazine: ''I completely understand and I agree. But it did make me a little impressed that they planned something together, and they were getting along and having fun as a team.''

Kim - who is expecting her fourth child via surrogate - admitted she worried about her children not being as close as she is to her own siblings.

She said ''I do worry about them getting along, because for my sisters and I, we were just so close growing up and obviously still are. And I want them to be, too!''