BEIRUT — Syrian villagers described watching rebels advance on their homes, as mortars thudded around them. By the end of the August attack, 190 civilians had been killed, including children, the elderly, and the handicapped, a human rights group said Friday in its most detailed account of alleged war crimes committed by those fighting the Damascus regime.
Human Rights Watch said the offensive against 14 pro-regime villages in Latakia province was planned and led by five Islamist extremist groups, including two linked to Al Qaeda. Other rebel groups, including those in the Free Syrian Army, a Western-backed alliance, participated in the campaign, but there is no evidence linking them to war crimes, the 105-page report said.
The new allegations are bound to heighten Western fears about those trying to topple Syrian President Bashar Assad and about who would take charge if they succeed.
‘‘It creates justifiable alarm that the opposition has been infiltrated and undermined by radicals,’’ said David L. Phillips, a former US State Department adviser on the Middle East.
The Free Syrian Army distanced itself from the five groups identified by HRW as the main perpetrators, saying it is not cooperating with extremists. ‘‘Anyone who commits such crimes will not belong to the revolution anymore,’’ said spokesman Louay Mikdad.
Human rights groups have said both sides in the civil war, now in its third year, have violated the rules of war, but UN investigators have said the scale and intensity of rebel abuses has not reached that of the regime.
The new allegations come at a time when the regime appears to be regaining some international legitimacy because of its seeming cooperation with a program to destroy Syria’s chemical weapons stockpile by mid-2014.
Human Rights Watch researcher Lama Fakih said rebel abuses in the Aug. 4-18 Latakia offensive are the ‘‘most egregious and widespread’’ violations by opposition fighters her group has documented in Syria.
‘‘They certainly amount to war crimes’’ and may even rise to the level of crimes against humanity, said Fakih, who visited the area a month after the attack, with regime permission.
The offensive targeted villages that are home to Alawites, or followers of an offshoot of Shi’ite Islam who form the backbone of Assad’s regime. Alawites are considered heretics by Sunni Muslim extremists among the rebels.
The rebels launched their attacks Aug. 4 at dawn, quickly seizing three regime military posts, Human Rights Watch said. Once those posts fell, no pro-government troops were left in the area and the rebels overran the villages, according to the report.
‘‘Witnesses described waking up to the sound of fighters coming into their villages, the sound of mortar and gunfire, and they frantically tried to leave,’’ said Fakih, who interviewed more than three dozen villagers, medical staff and officials from both sides.
Some could not run fast enough, witnesses said.
One man from a hamlet near the village of Blouta told Human Rights Watch he escaped with his mother, while black-clad rebels were shooting at them from two directions.
The man said he left his elderly father and 80-year-old blind aunt behind because of their disabilities. After regime forces retook the area, he said he returned home and found his father had been killed in his bed, and his aunt, Nassiba, in her room.