The incident in Peda village took place at around 8.15 AM, with groups of the two communities hurling stones at each other, police said, adding there was even firing between the clashing groups.
Four persons, aged between 27 and 30, were killed in the clash while at least 12 others were injured. Five seriously injured were taken to Meerut for treatment.
The accused fled the village after the incident. Eight women related to them have been detained for questioning, police said.
According to police, the girl was on her way to school when she was allegedly harassed by some youth belonging to another community.
A passerby objected to this act but he was beaten up by the accused, police said.
He then told some persons about the incident and soon a clash started, police said. There were reports of arson also.
Heavy police force has been deployed in the area in view of the incident.
DGP S Javeed Ahmed said the situation was under control and ADG (Law and Order) was at the spot, monitoring the developments.
Meanwhile, Chief Minister Akhilesh Yadav announced a compensation of Rs 20 lakh to the family of each of the deceased and Rs 5 lakh to the injured.
He also warned of strict action against those found guilty, an official release said