Two demonstrators, including a 14-year-old boy, were killed in Iraq's Kurdistan region when security forces opened fire on a protest by civil servants over unpaid salaries, officials and witnesses said Saturday.

The incident occurred on Friday in Qala Diza, a town near the border with Iran about 75 kilometres (45 miles) north of the city of Sulaimaniyah.

A budget crunch which has left many civil servants unpaid for months has sparked demonstrations in northern Iraq's autonomous Kurdish region, especially in areas dominated by the opposition.

Friday's protest escalated when demonstrators apparently changed the planned course of their march to head to the local headquarters of the ruling Kurdistan Democratic Party (KDP).

KDP guards responded to stone-throwing by opening fire, witnesses said, killing a 14-year-old boy and a 30-year-old teacher.

Medical sources in Qala Diza confirmed the deaths and said another 18 people were wounded. Angry demonstrators subsequently set fire to two KDP buildings.

"The police could have contained the demonstrators and made sure the guards did not fire straight at them but in the air," Ali Mohammed, a 35-year-old Qala Diza resident, told AFP.

Protests over salaries have mushroomed in areas such as Sulaimaniyah province, dominated by parties opposed to the KDP of acting regional president Massud Barzani and his nephew prime minister Nechirvan Barzani.

The demonstrations by unpaid civil servants come against the tense backdrop of a crisis that started in August, when Massud Barzani's presidential mandate expired and no deal was reached for his succession.