Unidentified militants lobbed a grenade at the house of Congress MLA M Oken Singh in interior Thoubal district of Manipur, but the explosive failed to detonate.
Official sources said on Thursday that Singh was at his official quarters when the incident took place on Wednesday.
This was the fourth attack on residences of MLAs in the last two weeks, the previous targets being O Joy Singh (Manipur People's Party), Y Sura Chandra (Congress) and L Nandakishore (Nationalist Congress Party).
The police said it would investigate if the incident was related to monetary demands made by militant organisations from legislators.
Following the attacks on MLAs, security personnel provided to legislators in the state have been put on alert, sources said.