The government said the murder would be investigated from "all angles including the hijab row".
Hours after the killing of a member of the rightwing Bajrang Dal in Karnataka's Shivamogga, the police made its first arrests.
CCTV footage has emerged of one man being arrested from the neighbourhood where Harsha, 25, was stabbed on Sunday night.
In the clip recorded at a little after 3 am early Monday, the man is searched by the police and then led away by them.
The police have arrested six people after questioning about a dozen people on the murder, which spurred violence and arson in Shivamogga yesterday.
"All the accused have been identified and are being traced. We will arrest everyone involved, only then we can say what the motive was behind the murder," said senior police officer Pratap Reddy.
The government said the murder would be investigated from "all angles including the hijab row".
Yesterday, the Karnataka government had ruled out any link to the row over hijab restrictions in schools and colleges, but state Home Minister Araga Dnyanendra said: "Organizations behind the hijab row are also under the scanner, their role is also being looked at. Legal action will be taken against those who engaged in stone pelting yesterday."
Violence broke out when Harsha's body was being taken for last rites in a procession. Over 5,000 people had joined the 8-km funeral procession.
As tension escalated, cars were set on fire and stone-pelting was reported. At least three persons, including a photo journalist and a policewoman, were injured. Several two-wheelers were either damaged or burnt.
The police had to fire teargas shells and use lathis to control the crowds. Schools and colleges were declared shut and large gatherings were banned.
The Karnataka government, facing questions over the procession being allowed in a volatile situation, distanced itself from the decision.
"Seeing (that there were a) lot of people visiting, the body was taken for last rites. It is the decision of the district administration," said the Home Minister, appealing for peace.
"We appeal to people not to allow any room for disturbing peace. The government will certainly arrest the criminals and get them punishment appropriately," said Mr Dnyanendra.
"These kind of murders should stop and it should end with Harsha's murder. This is the commitment of the government and the police department. We are taking this case to the logical end," the minister added.
The police have so far said Harsha was killed over "personal rivalry".
"As of now, we strongly believe this has happened with regard to previous enmity. Further investigations are on," said police officer K Thiyagarajan.
Several BJP leaders, including Karnataka Minister KS Eshwarappa and Union Minister of state Shobha Karandlaje, have alleged a conspiracy behind Harsha's murder and have demanded a National Investigation Agency (NIA) probe.
Mr Eshwarappa on Monday controversially blamed the murder on "Muslim goons" and accused Congress' Karnataka chief DK Shivakumar of instigating the killing with comments he had made at the height of the hijab protests.
"He was a very good worker. He was a young man who was an honest. Last night, Muslim goons murdered him. Recently, DK Shivakumar claimed that the national flag was replaced with saffron flag, and around 50 lakh saffron shawls was ordered from a factory in Surat for the anti-hijab protest. The goondaism has increased after he made these statements. We will not allow this goondaism to continue. We will extend all the help that we can to the man's family," Mr Eshwarappa told reporters.