Sweden’s government said on Wednesday it planned to introduce legislation requiring social media platforms like TikTok and Snapchat to take down criminal gangs’ ‘murder adverts’ within an hour or face hefty fines.

Criminal gangs active in Sweden increasingly use social media to recruit people to commit murders and other violent acts amid a surge in “crime as a service”.

The recruits are often children under the age of 15, Sweden’s age of criminal responsibility, meaning the youngsters cannot be...