Six months after television journalist Soumya Vishwanathan was shot dead, Delhi [Images] Police on Tuesday claimed to have cracked the case with the arrest of four youths who were also allegedly involved in last week's murder of a call centre executive.

Robbery is said to be the motive behind both the murders, which took place in a posh locality of Vasant Vihar in south Delhi within a span of six months. Both victims were returning from work in the wee hours when they were attacked.

Joint Commissioner of Police (South) Ajay Kashyap said in Jigisha's case the motive was 'purely to rob her and not to molest her'.

The official said recovery of the weapon used in the murder of call centre employee Jigisha Ghosh (28) on March 18 this year led to the cracking of the killing of  Vishwanathan (27).

"The weapons of offence used in committing the crime have been recovered. We are hundred per cent sure that the cases have been solved," Deputy Commissioner of Police (South) H G S Dhaliwal told PTI.

The arrested persons have been identified as Ravi, Baljit, Amit and Ajay. vmn

Vishwanathan was found shot dead in her car on September 30 last year while returning home after work around 3.30 am. The body of Ghosh was found in Faridabad on March 19.

In both cases, there were no signs of sexual assault. Police zeroed in on the accused on the basis of CCTV footage when they used Ghosh's ATM and credit cards to withdraw money and purchase expensive shoes and watches.

The arrest came following information that a group of criminals, who were allegedly involved in the murder of Ghosh, were moving around Nelson Mandela Marg near Vasant Vihar.

"We took three persons who were travelling in the vehicle into custody. They were picked up in connection with the murder case of Ghosh. During interrogation, they confessed they were also behind the murder of Vishwanathan," Kashyap said.

Initially, Kashyap said, the youths said they were innocent. "It was only when the investigation led to the recovery of weapons, there was a suspicion and further interrogation led to their admission of crime," he said.

On the Vishwanathan murder case, Kashyap said the gang was at the spot when they saw Vishwanathan travelling alone at a relatively slow speed.

"They followed her, the motive may have been perhaps robbery, molest or eve tease her. It is still to be verified," he said.

The gang followed her for a while and there was an exchange of words.

"She may have reacted and provoked them. Ravi allegedly took out his country-made pistol and fired a single shot at her and unfortunately that proved to be fatal as it hit her on the head," he said.