By Michelle Nichols
UNITED NATIONS (Reuters) - U.S.-based Physicians for Human Rights on Wednesday blamed Syrian government forces for 88 percent of its recorded attacks on hospitals and almost all recorded killings of medical workers during the country's four-year conflict.
As the war enters its fifth year, the group said that Islamic State militants, who have captured swathes of territory in Syria and Iraq, have executed four health professionals and six attacks on medical facilities in the past 17 months.
"To be clear, that these numbers are significantly lower than those by the government does not make these acts less criminal. Each execution of a doctor and each attack on a health facility is a war crime," Widney Brown, Physicians for Human Rights' director of programs, told a news conference.
Syria's U.N. mission was not immediately available to comment.
Brown said each attack and death documented by the group had been confirmed by three independent sources and corroborated using satellite imagery before and after the dates of the attack and through sources in the field.
In a new report, the group accused Syrian government forces of being responsible for 97 percent of the unlawful killings of 610 medical personnel. Physicians for Human Rights said 139 of those deaths were a result of torture or execution.
Brown said the group used experts to establish what weapons were used in each attack, which allowed them to apportion blame.
In the past four years there were 233 illegal attacks on 183 medical facilities, of which Syrian government forces were responsible for 88 percent, Physicians for Human Rights said.
"The United Nations Security Council has utterly failed in its duties. These crimes rightly belong before the International Criminal Court," said Susannah Sirkin, Physicians for Human Rights' director of international policy and partnerships.
Russia and China vetoed a bid in May last year to refer the situation in Syria to the International Criminal Court for possible prosecution of war crimes and crimes against humanity committed during the civil war.
More than 210,000 people have died in Syria's conflict, which began when peaceful protests against President Bashar al-Assad in March 2011 degenerated into an armed insurgency following a fierce security crackdown.
The United Nations says some 12.2 million Syrians need assistance, while 3.8 million people have fled the country and about 7.6 million in Syria are displaced.
(In 2nd paragraph, Physicians for Human Rights corrects number of attacks on medical facilities blamed on Islamic State to six, not 16)
(Reporting by Michelle Nichols; Editing by Leslie Adler)