Iraqi Agriculture Minister Ezzedine al-Dawleh resigned on Friday after a protester was killed in the north, the second minister from the Sunni-backed Iraqiya bloc to quit this month.
Prime Minister Nuri al-Maliki, a Shiite, is at loggerheads with Iraqiya, which is a part of his national unity government, over its accusations against him of authoritarianism and sectarianism.
"I stand in front of my people... in Nineveh and I announce that I resign from this government, because there is no way I can continue in a government that does not respond to the demands" of the people, Dawleh told a televised news conference alongside parliament speaker Osama al-Nujaifi.
Deputy Prime Minister Saleh al-Mutlak told AFP that Dawleh, who was born in Nineveh province, had been considering the move for some time, but that a deadly shooting by security forces at a protest in northern Iraq brought the issue to head.
A high-ranking official in the Nineveh governor's office said one protester was killed and five wounded on Friday, and that an investigation was underway.
Meanwhile, activists said at least one demonstrator was killed when security forces fired on an anti-government protest in Mosul, the capital of Nineveh.
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A police officer said protesters began throwing stones at security forces after Sheikh Hussein al-Obaid al-Juburi, a supporter of the demonstrations, was arrested at the square on terrorism charges.
A policeman fired in the air in an effort to disperse them, and when they continued throwing stones, other police opened fire, the officer said.
"Weapons should not be used against the protesters, and this is a clear crime," Nujaifi, also from Iraqiya, told the news conference.
Finance Minister Rafa al-Essawi, a leading Sunni and Iraqiya member, announced his resignation at an anti-government demonstration on March 1.
Protesters have taken to the streets in Sunni-majority areas for more than two months, calling for Maliki's resignation and decrying the alleged targeting of their minority community by the Shiite-led authorities.
The protests were initially sparked by the arrest of several of Essawi's guards on terrorism charges in December, but have since expanded markedly.
The government has sought to curtail demonstrations by saying it has released thousands of detainees and raised the salaries of the Sahwa anti-Qaeda militiamen, and also by employing security forces.
Friday was not the first time security forces have fired on protesters. S -- soldiers killed eight demonstrators near Fallujah on January 25.