Five people died during demonstrations over unpaid civil servant salaries and rising tensions with Baghdad in the Kurdish city of Rania in Sulaymaniyah province, according to Miran Mohammad, the provincial health director.
Another person died while undergoing treatment at a hospital, said a security source who spoke on the condition of anonymity because he's not authorized to speak to the media.
Iraqi Kurds have built a semi-autonomous region in northern Iraq with their own regional government, the Kurdistan Regional Government, or KRG, their own armed forces and an oil-dependent economy.
Kurds -- most of whom reside in Middle East countries, including northern Iraq, eastern Turkey, western Iran and small portions of northern Syria and Armenia -- do not have an official homeland or country. They have never achieved nation-state status. In Iraq, portions of the region are recognized by Baghdad.
Some Kurdish security forces were injured in Rania after demonstrators hurled stones and set political party buildings on fire, the source told CNN.
KRG Prime Minister Nechirvan Barzani appealed for calm, in a statement posted on his official Facebook page.
"Your frustrations are understandable, and I hear them," he wrote. "Peaceful expression of views is, of course, a legitimate and democratic right. But violence is never acceptable. I call on all of you to conduct your protests peacefully."
The protests started Monday -- including in the cities of Sulaymaniyah and Halabja -- as Kurdish civil servants demanded unpaid salaries and other demonstrators angrily called for better water, power and other public services.
The KRG condemned the violence in a statement, saying it sabotaged security and stability.
The government said it recognized citizens' right to protests and expressed concern over "activities that were not a part of civilian movements" that contributed to the violence, especially in Sulaymaniyah province.
The statement noted that buildings connected to the government and political parties had been targeted, leading to injuries and property damage.
Videos on social media appeared to show protesters setting fire to buildings connected to the government, as well as the Patriotic Union of Kurdistan (PUK) and Kurdish Democratic Party of Iraq (KDP) in Sulaymaniyah, Kuya and Taktak. Tires and cars also were set ablaze.
Some video appeared to show cheering crowds as demonstrators torched posters of former Kurdish president Masoud Barzani. Heavy gun fire, presumably from Kurdish security forces, can be heard in some videos.
CNN could not independently verify the authenticity of the social media posts.
The regional government has been in financial straits since 2014. Baghdad reduced funding to the region when the KRG decided to bypass the central government and moved ahead with a controversial plan for a Kurdish -controlled pipeline to carry oil from Kirkuk to Turkey.
The KRG has been struggling to pay public sector salaries since a contentious independence referendum in September.
Baghdad regained control of disputed oil-rich fields in Kirkuk. In addition, the region has reeled from the cancellation of international flights as well as increasingly strained relations with neighboring Turkey and Iran.
Kirkuk is critical to the government coffers of both the KRG and the Iraqi government in Baghdad.
Kurdish forces gained control of the mutli-ethnic city after Iraqi government forces abandoned it during the ISIS offensive in 2014.