While a journalist with IBN7 television channel, Rajesh Verma, was killed in crossfire between rival groups, a mob lynched a photographer working for police. Four more people died after the clashes spread.
Meanwhile, a home department official said the army has been moved in to help the administration maintain law and order.
A TV journalist and a police photographer were among the 9 killed in the clashes
As many as 28 companies of security forces including Rapid Action Force (RAF) and Provincial Armed Constabulary (PAC), have also been rushed to the violence-hit areas.
Additional Director General of Police (Law and Order) Arun Kumar told IANS that Inapector Generals of Police (Meerut) and (Law and Order) has been asked to camp in Muzaffarnagar and try to normalise the situation.
Police officials said more than 34 people were injured in the clashes that erupted after a mahapanchayat at an inter college in Nangla Mandaud.
Elders of two religious groups were meeting to sort out the simmering tension between the two communities ever since three youngsters were killed Aug 27 over case of harassment.
Police said a bus headed for the mahapanchayat was stoned near Basi village, resulting in injuries to six people. As news spread, people of both communities pelted stones at each other.
Stone pelting was also reported from Basiyakala village in which four people were killed and five others were injured.
At the mahapanchayat, it was decided that strict action be taken against the killers of Sachin and Gaurav, the two youth killed Aug 27.
It was also decided that people will themselves deal with eve-teasing cases and not seek help of police. Moreover, decision of the "khaap" would be final in such cases.
Police said more than three dozen people were rounded up after the violence and curfew clamped in Civil Lines, Nai Mandi and Kotwali police station areas.
Tension gripped the area Aug 27 after two communities clashed over an alleged molestation incident in which one person was killed and in the fallout, a mob lynched two others in Kaval area.
As tension grew, police tried to intervene and even Director General of Police (DGP) Devraj Nagar visited Muzaffarnagar Friday to take stock of the security arrangements.
Chief Minister Akhilesh Yadav, meanwhile, expressed sorrow at the death of six people, including a journalist. "The guilty will not be spared, all efforts are being made to bring the situation under control," he said.
The chief minister's office informed an ex-gratia of Rs.10 lakh will be given to the family of the deceased journalist while the next of kin of the other deceased will get Rs.5 lakh each. The seriously injured and those with minor injuries will receive Rs.50,000 and Rs.20,000 each, respectively.
The Uttar Pradesh Accredited Journalist Association condemned Rajesh Verma's killing. President Hemant Tiwari and secretary Siddharth Kalhans said the killing of a scribe was unfortunate and demanded enhanced security for journalists.