Massive clashes between Syrian security forces and loyalists of ousted President Bashar Assad as well as revenge killings for two days left more than 1,000 people dead, media reports said on Sunday.

 The clashes have been deemed one of the deadliest acts of violence since Syria's conflict began 14 years ago.

Besides 745 deceased civilians, 125 government security force members and 148 militants affiliated with Assad were killed as well, AP reported quoting a Britain-based Syrian Observatory for Human Rights.

It added that electricity and drinking water were cut off in large areas around the city of Latakia.

The clashes, which erupted on Thursday, marked a major escalation in the challenge to the new government in Damascus.

This comes three months after insurgents took authority after removing Assad from power.

The government has said that they were responding to attacks from remnants of Assad's forces and blamed "individual actions" for the rampant violence.

The revenge killings were started by Sunni Muslim gunmen loyal to the government against members of Assad's minority Alawite sect on Friday which is seen as a major blow to Hayat Tahrir al-Sham, the faction that led the overthrow of the former government, AP reported.

Alawites made up a large part of Assad's support base for decades.

Residents of Alawite villages and towns spoke to The Associated Press about killings during which gunmen shot Alawites, the majority of them men, in the streets or at the gates of their homes.

Many homes of Alawites were looted and then set on fire in different areas, two residents of Syria's coastal region told the AP from their hideouts.

They asked that their names not be made public out of fear of being killed by gunmen, adding that thousands of people have fled to nearby mountains for safety.