(CNN) -- Syrian security forces were commanded to shoot unarmed protesters, according to military and security agency defectors interviewed by a human rights watchdog.
Human Rights Watch said Saturday that they "described receiving, and following, orders to shoot on protesters to disperse them."
Efforts to reach the Syrian government for comment were not immediately successful.
The group said they interviewed eight soldiers and four members of the security agencies in Lebanon, Turkey and Jordan who defected over the last four months of anti-government protests.
"The testimony of these defectors provides further evidence that the killing of protesters was no accident but a result of a deliberate policy by senior figures in Syria to use deadly force to disperse protesters," Sarah Leah Whitson, Middle East director at Human Rights Watch, quoted in the report.
"Syrian soldiers and officials should know that they too have not just a right but a duty to refuse such unlawful orders, and that those who deliberately kill or injure peaceful protesters will be subject to prosecution."
The claims coincide with ongoing assertions by Syrian activists that security personnel have assaulted unarmed protesters. The Syrian regime claims armed groups are responsible for the violence at the demonstrations, which erupted nationwide in mid-March.
There was a flurry of deaths on Friday during nationwide protests. The Syrian Observatory for Human Rights, an activist group, said 1,410 civilian and 348 members of army and security forces have been killed over the last four months.
The people interviewed "participated in the government crackdown in Daraa, Izraa, Baniyas, Homs, Jisr al-Shugur, Aleppo, and Damascus" and witnessed "the shooting and injury of dozens of protesters, and the arbitrary arrest and detention of hundreds."
All of those interviewed defectors said "their superiors had told them that they were fighting infiltrators (mundaseen), Salafists, and terrorists. The defectors said they were surprised to encounter unarmed protesters instead, but still were ordered to fire on them in a number of instances," a Human Rights Watch report said.
"The defectors also reported that those who refused orders to shoot on protesters ran the risk of being shot themselves. One of the defectors reported seeing a military officer shoot and kill two soldiers in Daraa for refusing orders."
The United States and other countries have denounced Syria's tough crackdown on peaceful protests, and a visit to the restive city of Hama by the U.S. ambassador to Syria this week has drawn sharp criticism from the Bashar al-Assad regime.
Government officials said Ambassador Robert Ford incited protest in Hama, a claim called "absolute rubbish" by State Department's spokeswoman Victoria Nuland. Syrian officials also claimed he didn't get proper permission to travel, an assertion also disputed by the United States.
Hama has been the scene of large anti-government demonstrations and a crackdown this week by government forces.
Syria's minister of Islamic Endowments was the latest to denounce Ford's presence in Hama, saying it was "without prior permission considering that it was primarily intended to incite bloodshed and ruin the contacts designed to stop bloodshed and eliminate sedition," according to the state-run Syrian Arab News Agency.
Citing remarks of Abdul-Sattar al-Sayyed, SANA said the "U.S. ambassador wants Jerusalem to be an eternal capital of Israel, adding that the U.S. has always been against Arabism, Islam and values."
CNN's Yousuf Basil and Jomana Karadsheh contributed to this report