* 190 men, women and children killed in rebel offensive - HRW
* Mass graves seen by Human Rights Watch researcher
* Western-backed rebels were involved in broader campaign
By Oliver Holmes
BEIRUT, Oct 11 (Reuters) - Syrian rebels killed at least 190 civilians and took more than 200 hostage during an offensive in Latakia province in August, Human Rights Watch said on Friday, in what it calls the first evidence of crimes against humanity by opposition forces.
HRW said many of the dead had been executed by militant groups, some linked to al Qaeda, who overran army positions at dawn on Aug. 4 and then moved into 10 villages nearby where members of President Bashar al-Assad's Alawite sect lived.
In its first government-sanctioned trip into Syria during the 2-1/2-year conflict, New York-based HRW has documented a series of sectarian mass killings by Assad's foes during a broader campaign in which Western-backed rebels took part.
In some cases, entire families were executed or gunned down as they fled, according to a report titled "You Can Still See Their Blood".
HRW identified five rebel groups instrumental to funding, organising, planning and carrying out the Latakia attacks, including the al Qaeda-linked Jabhat al-Nusra and Islamic State of Iraq and the Levant groups, as well as the Islamist group Ahrar al-Sham and another unit of foreign jihadi fighters.
These groups publicised their involvement through videos and statements, some of which were used to corroborate the HRW report. The operation appeared to have been largely financed by private Gulf-based donors, HRW said.
What is less clear is the role of fighters from the Free Syrian Army (FSA), the armed wing of the main opposition coalition which is openly supported by the United States, Britain, France and Sunni Muslim Gulf states.
In a video posted on Aug. 11 and apparently filmed in Latakia, FSA chief Salim Idriss said the body was participating in the offensive "to a great extent."
But HRW researcher Lama Fakih, who spent several days in Latakia province in September and spoke to residents, soldiers, militiamen, doctors and officials, said she could not confirm if the FSA were present on Aug. 4 when the atrocities took place.
Assad's forces are also accused by rights groups of committing atrocities and using incendiary and cluster bombs in populated areas. They have carried out sectarian attacks, including killing up to 450 civilians in two massacres in mainly Sunni Muslim areas in May, according to U.N. officials.
The opposition and rights groups accuse Damascus of a chemical weapons strike in a Damascus suburb on Aug. 21 that killed hundreds of civilians. The government blames the attack on rebels.
Reuters was unable to get comment from all 20 rebel groups mentioned in the HRW report. Syrian National Coalition spokesman Khaled Saleh said the SNC condemns all human rights abuses and if any had been committed by rebels affiliated with the coalition, they would face justice.
A member of the Sunni Islamist Ahrar al-Sham said its fighters had killed no civilians in the offensive. "If someone uses a weapon against you, you have to fight them. If they do not, you must not kill them," said Abu Muhammed al-Husseini, the 30-year-old head of Ahrar al-Sham's political office in Raqqa.
In a written statement to Reuters, the SNC's Saleh said: "We have previously committed ourselves to applying these rules on all the brigades that work for us and we will hold accountable, after investigation and fair trial, all those responsible for violations against human rights or international laws. The incidents in Latakia are not an exception and we will treat them as we treated previous cases."
Lama Fakih, the Syria and Lebanon researcher in HRW's Middle East and North Africa Division, told Reuters in reference to the Latakia operation by rebels: "Homes were destroyed and burned. Most villagers had not returned."
Fakih met Hassan Shebli, an Alawite man from the village of Barouda, who fled his village at 4:30 a.m. on Aug. 4 as rebels approached. He left his wife, who was in her 60s and needed canes to walk, and his son, 23, who was paralysed, Fakih said.
Shebli said that they were both killed and buried behind his house. Fakih visited the house and saw bullet holes in the son's bed frame. "I was able to see the blood splattered on the wall," she said, showing a picture of the room.
Rebel footage posted on the Internet showed images of Shebli's son and wife with rebel fighters during the operation.
The scale and organisation of the attacks on civilians suggest premeditation and make them a crime against humanity, HRW said, rather than isolated war crimes reported during the Syrian civil war. The United Nations says the conflict has killed more than 100,000 people in two-and-a-half years.
"These abuses were not the actions of rogue fighters," said Joe Stork, acting Middle East director at Human Rights Watch. "This operation was a coordinated, planned attack on the civilian population in these Alawite villages."
Residents who returned to the villages said they found bodies of residents on the streets, in their homes as well as in piles of burnt corpses and in mass graves, according to Fakih.
Syria's mainly Sunni Muslim rebels are battling to overthrow Assad, whose Alawite sect is an offshoot of Shi'ite Islam and accounts for about 12 percent of Syria's 23 million people. The conflict erupted in 2011 when mainly peaceful protests against four decades of Assad family rule were put down with force.
The HRW report documented the involvement of over 20 rebel groups in the Latakia offensive, which started on Aug. 4 after months of bombardment of a nearby Sunni village, and ended on Aug. 18, when the government regained control of the area.
Rebels told Reuters in August that around 200 of Assad's men were killed at the start of the offensive. (Editing by Mark Heinrich)
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