Every war brings a new terror. In recent weeks so-called "barrel bombs" dropped from helicopters into rebel-held areas have emerged as the latest weapon of terror to kill and maim thousands of mostly innocent civilians.

But now some rebel leaders are hinting the reign of terror brought on by the barrel bombs, assembled and deployed by forces loyal to Syrian President Bashar al Assad, could be coming to an end.

Syria Barrel Bombs Sow Terror

Syrian opposition leader Ahmad Jarba told a Middle East television news station a few days ago that advanced arms are en route, including weapons designed to help opposition “get rid of these aircraft” — the government helicopters and warplanes that dump the explosives- or fuel-laden barrels over rebel territory.

Syria Barrel Bombs Sow Terror

He would not say which countries would supply the missiles that rebels have long urged foreign backers to provide.

Syria Barrel Bombs Sow Terror

?The day before Jarba’s interview U.S. Secretary of State John Kerry forcefully condemned an increased use by the Assad regime of crude-but-deadly barrel-bombs, especially on rebel-held districts in the Syrian city of Aleppo.

“Each and every barrel bomb filled with metal shrapnel and fuel launched against innocent Syrians underscores the barbarity of a regime that has turned its country into a super magnet for terror,” Kerry said in remarks issued by the State Department.

On February 4, the Syrian opposition activists accused the regime of dropping a bomb on the Ottoman Bin Affan mosque in Aleppo, which was being used as a school. Fifteen boys were killed in the attack.

The U.S. and other Western governments sympathetic to the anti-Assad uprising have held back from supplying rebels with portable surface-to-air missiles, often called SAMS or MANPADS, for “Man-Portable-Air-Defense-System.”

One reason cited by U.S. officials in the past is that such missiles, capable of shooting down a commercial aircraft, could fall into the hands of terrorists or foreign Jihadists. And rebel commanders and Western diplomats say Washington had urged the Gulf countries of Saudi Arabia and Qatar not to provide them to the rebels.

Rebels have managed to secure some MANPADS on the black market, but not in sizeable quantities, they say.

Opposition activists say there has been a clear uptick in the use of barrel bombs in recent weeks, starting in December in the run-up to the Geneva 2 peace talks.

This week activists posted harrowing online footage of the crude devices being dropped on the southern Damascus suburb of Daraya during the Geneva 2 peace talks, the first round of which ended without agreement amid bitter recriminations between the warring sides.

And government forces have been pounding several rebel-held areas of Aleppo with barrel bombs. Aleppo has been divided since rebels captured several districts in 2012, but government forces have started a new offensive on eastern approaches to the city. According to the Syrian Observatory for Human Rights, a U.K.-based pro-opposition monitoring group that relies on a network of informants inside Syria, as many as a hundred people have been killed by barrel-bombs in Aleppo over the past few days.

Another rights group, the Violation Documentation Center, says that of the 433 people killed in Aleppo province airstrikes between November 22 and December 18, only eight were rebel fighters.

According to rights groups, the bombs, first used in August 2012, are rudimentary devices made from oil drums or cylindrical containers packed with TNT and an assortment of metal parts, steel fragments or fuel, which are then topped off with a basic fuse that detonates on impact. Not equipped with any kind of guidance system, the bombs are simply rolled out of helicopters.

According to Richard Lloyd, a technology consultant, the bombs are a cost-effective way of striking at built-up areas and sowing terror by killing arbitrarily.

“The main objective of the Syrian barrel bomb program is to provide cheap and lethal damage on urban areas in Syria,” Lloyd wrote in a post for the influential

But according to Peter Quentin of the Royal United Services Institute, who spoke via Skype, cost isn't the only factor that makes improvised devices Damascus's weapon of choice.

“I would say these are all about the symbolism, the psychological destructive nature of this," he said. "It’s the terrorizing of a population.”

Experts say barrel bombs are impossible to aim accurately and become increasingly indiscriminate as government aircraft fly higher to avoid rebel fire. A new innovation, altitude-sensitive fuses, make the bombs explode before they hit the ground, causing even more widespread damage.