Just before leaving Syria late last month, U.N. weapons inspectors discovered an odd-looking projectile sticking out of the dirt near the spot where hundreds of Syrians died Aug. 21. Experts who studied the device would call it a “trash can on a rocket,” citing its long fuselage and fat warhead capable of carrying 15 gallons of poison.

The reference to the rocket’s discovery would take up only a few lines in Monday’s highly technical U.N. report confirming the use of lethal sarin gas against Syrian civilians. But the new details about one of the weapons allegedly used in the attack came closer than ever to pinning the blame on the Syrian government, diplomats and weapons experts said.

The 38-page U.N. report concluded that much of the sarin used in the attack was hurled east of Damascus in unusually shaped, 330mm artillery rockets, similar to the one found protruding from the soil in the Zamalka suburb. The finding is significant, weapons experts say, because the rockets appear to be of a unique Syrian design, different from any of the shells and warheads associated with other producers of chemical arms.

The size of the warhead — capable of carrying more than 20 times as much liquid as other commonly used munitions — could account for the unexpectedly large number of deaths from the Aug. 21 attack, in which more than 1,000 people are estimated to have died, diplomats and weapons experts said.

Moreover, the 330mm rocket and its Iranian-built launching system are known to be tightly controlled by Syrian forces. Since the conflict began, there have been only a handful of accounts of government forces using such rockets and no reports of rebels acquiring either the weapons or the specialized launching tubes required to fire them, experts say.


How the intelligence stacks up

“The U.N. report provides solid confirmation as to the . . . rockets used in the attack, and its evidence provides even greater proof that the government was responsible,” said Peter Bouckaert, emergencies program director at Human Rights Watch, which last week issued a study that also pointed to the rockets as vital clues linking the Syrian regime to the attack.

Although the U.N. report does not explicitly assign blame, Bouckaert said, its findings “point even more convincingly towards Syrian government responsibility,” citing not only the rockets’ remnants but also their flight path and the military-­grade quality of the sarin that they contained.

“It points the finger directly at them,” he said.

The U.N. team’s report was the first official document to confirm the use of the unusual rockets, which have been cited in several reports by human rights activists and weapons experts who analyzed images of rocket motors and other parts found in neighborhoods hit by toxic gases in the pre-dawn hours of Aug. 21. Chemical warheads typically contain only a small amount of explosives — enough to disperse, but not incinerate, their toxic contents — and several of the rockets were relatively intact when U.N. investigators toured the affected neighborhoods last month.

In the Moadamiya suburb, inspectors found the remains of several Russian-made 140mm rockets, many of them bearing identification plates and engravings in the Cyrillic script, according to the U.N. report. It said the larger, 330mm rockets were found in Zamalka and Ein Tarma, two southeastern neighborhoods that recorded the highest numbers of casualties.

The report included photographs and drawings of the 330mm rockets’ barrel-shaped warhead, which it described as being about 14 inches wide and 30 inches long. At those dimensions, the weapon’s carrying capacity would have been about 120 pounds of liquid sarin, the report said.

Environmental samples from the rocket remnants and surrounding soil tested positive for sarin, the report said.

Researchers who have studied the weapons used during the Syrian conflict confirmed that the 330mm rockets have been used rarely, and always by government forces. Human Rights Watch’s weapons experts described the rocket as crude but effective, with a non-aerodynamic design that make it unsuitable for longer-range attacks.

“The rocket would be relatively short ranged and not capable of accurate targeting,” the group said in its report, released Sept. 10.

The warhead is not listed in any of the standard reference guides for international weapons systems and appears to be “locally but industrially produced,” the group said. It cited amateur videos showing Syrian forces apparently launching a high-explosives variation of the same rocket using truck-mounted launchers.

“The only known documented attacks using this weapon system in Syria have been against opposition-­held areas and targets,” it said.

At least eight of the rockets fell in Zalmalka, a densely populated residential area that reported more than 700 deaths from poison gas. One witness interviewed by Human Rights Watch said the projectiles hit with “a low sound,” not with the thunderclap and devastation of a conventional artillery rocket.

“I didn’t reach the explosion site because I saw injured people on the ground and people running and screaming in all directions,” the witness was quoted as saying. “The house was not destroyed . . . but they were dead on the ground.”

Some of the rockets slammed through buildings and punctured walls, allowing U.N. officials to make crude calculations about their flight path. The report concluded that the rockets were fired from the northwest, consistent with the reports of Western intelligence officials who said the attack was launched from government-held positions north of Damascus or near the city center.

The Obama administration’s representative to the United Nations, Samantha Power, singled out the U.N. report’s finding on munitions in brief comments to reporters.

“We have reviewed thousands of open-source videos related to the current conflict in Syria,” Power said, “and have not observed the opposition manufacturing or using this style of rocket.”

She also noted the report’s findings about the quality of the nerve gas found in environmental sampling — a grade of sarin higher than that used in a similar program run by Iraq’s Saddam Hussein.

“The weapons obtained on the site . . . of this monstrous crime were professionally made,” she said.