State media have said their forces were seeking only to clear the area of "terrorists," the term they have routinely used when referring to rebel forces.
But the U.S. State Department said it was "appalled by horrific reports that more than 100 people were killed May 2" in Beyda, a suburb of Baniyas.
Several opposition groups said largely Alawite government forces used tanks, battleships and missile launchers to target largely Sunni neighborhoods in and around the coastal city of Baniyas.
Government forces killed at least 200 people on Friday and Saturday in Baniyas and its suburbs, the opposition Local Coordination Committees said Saturday.
But reliable information has been difficult to obtain because government forces controlled access to the village, the LCC said.
A graphic video posted by activists who said it was shot in the Ras al-Nabaa neighborhood showed people, including an infant, lying lifeless on the ground. Many bore what appeared to be bullet wounds, and some appeared burned.
CNN has not been able to confirm the video's authenticity, as access to Syrian war zones has been severely limited by the government.