Unidentified miscreants hurled the hand grenade on the roof of the house on Tangkhul Avenue which exploded injuring three tenants last night.
The injured were admitted to a hospital and their condition is stated to be stable, police said.
One SUV was also damaged in the blast.
Nimreih Shimray, owner of the house, said he was served a demand note of Rs 3 lakh by a militant outfit two weeks back.
Shimray is the president of a contractor's association based in Ukhrul district of Manipur.