Ludhiana, April 23 -- Police have registered a case after an unidentified individual, claiming to be a close associate of gangster Lakhbir Singh Landa, allegedly threatened a city-based builder with a grenade attack if he failed to pay Rs.5 crore as extortion money. The incident unfolded between April 16 and 19 when the builder, whose identity is being withheld for security reasons, received multiple threatening calls and voice messages from an unknown international number....