THIRUVANANTHAPURAM, Aug. 19 -- A 13-year-old girl allegedly planned the murder of her 65-year-old grandfather in Kerala's Alappuzha district with her 17-year-old boyfriend and two of his friends to steal gold and other valuables, police said on Tuesday. The four allegedly planned to sell the gold and use the money to buy iPhones and bikes, they said.

The girl stayed in a separate house with other relatives, while her grandfather, Sivankutty Chettiyar, lived alone in a rented house in Karuvatta village, officials aware of the matter said. Other family members were out of town when the alleged murder took place on August 15, they added.

"The girl, her boyfriend and the two other boys, aged 16 and 17, were detained on Tuesday for their all...