The human rights group's report came as Jordanian and U.N. officials opened a second refugee camp for Syrians fleeing the carnage.
In its report, "Death from the Skies: Deliberate and Indiscriminate Airstrikes on Civilians," released Wednesday, HRW said it documented at least 152 citizens died in government airstrikes in opposition-controlled areas in Aleppo, Idlib and Latakia provinces.
HRW said it visited 50 sites and talked to 140 witnesses and victims.
"In village after village, we found a civilian population terrified by their country's own air force," said Ole Solvang, a Human Rights Watch emergencies researcher who visited the sites and conducted many of the interviews. "These illegal airstrikes killed and injured many civilians and sowed a path of destruction, fear, and displacement."
Local Syrian activists said airstrikes have killed more than 4,300 civilians throughout Syria since July 2012.
Human Rights Watch said Syrian forces also dropped unguided bombs from high-flying helicopters, and documented use of incendiary weapons and more than 150 cluster bombs.
The Free Syrian Army and other Syrian armed opposition groups did not take all measures to avoid deploying forces and facilities such as headquarters in or near densely populated areas, the rights organization said.
Human Rights Watch said it believed the information contained in its report should "assist those seeking to bring the perpetrators of these crimes to justice."
It also called on governments and companies to stop selling or supplying weapons, ammunition and material to Syria.
The influx of Syrian refugees into Jordan prompted the U.N. refugee agency to open a second camp as an official warned the crisis had hit a "breaking point."
The desert Mrajeeb al-Fhood camp, 23 miles from the Syrian border, received more than 100 Syrians its first day and will initially hold about 4,500 to 5,000 refugees, with plans to increase its size to accommodate about 25,000, Andrew Harper, the U.N. refugee agency representative in Jordan, told the Los Angeles Times.
"It's been built to a much higher standard" than the packed Zaatari camp 50 miles northeast of Amman, which was intended for 50,000 refugees but hosts more than twice that number, Harper said.
Riots and protests have erupted at the crowded Zaatari camp, which has grown to become equivalent in population to Jordan's sixth-largest city, after the far-northwest city of Ar Ramtha, a United Press International calculation indicates.
The Times said Zaatari has become notorious for its harsh conditions, including crime and drugs.
Some refugees returned to Syria, preferring to risk the perils of war. Zaatari is run by Jordan and the U.N. refugee agency.
Mrajeeb al-Fhood -- funded by the United Arab Emirates and run by its Red Crescent Society -- is meant to ease pressures on Zaatari, Harper said.
"It's a welcome step to accommodate refugees," he said. "But we have to build other camps. ... The support has not matched the massive influx."
It would likely take two months before his agency, officially known as the Office of the United Nations High Commissioner for Refugees, can open a third camp, Harper told the Times.
The agency is currently building roads and drilling wells for a third camp.
More than 1.3 million Syrian refugees have fled to Jordan, Turkey, Lebanon and Iraq, with the number likely to top 4 million in the next eight months, the U.N. refugee agency said.
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