Thiruvananthapuram: Three engineering students were among five arrested here Saturday in connection with the murder of diamond trader Harihara Varma on December 24.
Additional Director General of Police A Hemachandran told reporters here that all of those arrested were from Kerala.
The three students, one of whom was the mastermind behind the murder, were studying in a Bangalore college, he said.
The ADGP said robbery was the motive behind the murder and added that media reports putting the value of the stolen diamonds at Rs 300 crore was not correct.
"The diamonds taken away from him on that date were not as valued as reported in the media," he said.
Harihara Varma, 55 was found murdered in his house at Puthoorkonam at nearby Vattiyoorkavu.
Police had received vital clues from the driver of the car in which they went to Varma's house posing as buyers of diamond.
The incident came to light after one Haridas, an advocate by profession and who claimed to be a mediator for the trade, informed police about the murder.
The Kerala government had set up a special police team, headed by DCP Putta Vimaladitya, to probe the case.