The mother and the grandfather of a 21-year-old woman have been arrested on the charge of murdering her and her infant son in a case of suspected 'honour killing', police said.

Deepika and her four-month-old son were smothered to death at Thamasandra village in Ramanagaram district, about 60 km from Bangalore, on the night of Feb 26 and their bodies were cremated immediately, police said.