In a major breakthrough, fugitive Khalistani preacher Amritpal Singh's close aide Papalpreet Singh was arrested from Punjab's Hoshiarpur on Monday. Papalpreet was arrested in a joint operation by the Punjab and Delhi Police that also involved their counter-intelligence wings. Papalpreet is considered to be Amritpal's mentor and is alleged to have links with Pakistan's ISI. Amritpal and Papalpreet had been on the run since March 18 when the Punjab Police launched a crackdown against the Khalistan sympathiser and his aides.