Besides the two arrested men, certain others were under custody, the police said. (Representational)

The Crime Branch Thursday took over the investigation into the killing of two Youth Congress workers, as the total number of arrests in the case climbed to seven with five more people being arrested, police said.

The arrest of K M Suresh, K Anil Kumar, M Ashwin, Sreerag and G Sreejan was recorded Thursday, they said. Local CPI(M) leader, A Peethambaran and Saji George were arrested in the last two days.

A police press release said the case relating to the killings has been handed over to the Crime branch as per the direction of the DGP Loknath Behera.

In a setback to the ruling Communist Party of India (Marxist), its local committee member Peethambaran was arrested on Tuesday in connection with the killings of Youth Congress activists Kripesh, 24 and Sarath Lal, 21, on Sunday night.

Soon after Peethambaran's arrest, the Kasaragod district committee of the CPI(M) expelled him from the party, following directions from the state committee.

Meanwhile, the parents of the killed activists demanded a CBI probe into the incident and reiterated the allegation that the killings were executed with the support and knowledge of the CPI(M).

The parents said they had no confidence in the police investigation. Putting more pressure on the Left party, television channels on Thursday aired a purported speech of V P P Mustafa, a local CPI(M) leader, threatening Congress activists during a party meeting at nearby Kallyat a month ago.

In the clip, Mustafa is purportedly heard saying everyone knew the CPI-M's style of functioning and how the party reacted when it ran out of patience.

The Congress alleged that the speech indicated that the killings were executed with the support of the CPI(M) leadership.

Kripesh and Sarath Lal, in their early twenties, were waylaid and attacked when they were returning home after attending a function at Periya in Kasaragod district on Sunday night.

The opposition Congress and the BJP have alleged that the killings were executed with the knowledge and support of the CPI (M) leadership, which the Left party has denied.