BAGHDAD — A newly elected member of Iraq’s Parliament was shot and killed in northern Iraq on Monday night.

The candidate, Bashar Mohammed Hamid, a Sunni mill owner from Mosul, had run with the electoral coalition of Ayad Allawi, a former interim prime minister. The coalition, Iraqiya, narrowly defeated Prime Minister Nuri Kamal al-Maliki’s bloc, according to preliminary results still in dispute more than two and a half months after the election.

Mr. Hamid, 35, is the first candidate for Iraq’s new 325-member Parliament to become a direct target of the violence, and his killing threatened to add tension to the nation’s unsettled politics.

On the same day, election officials disclosed that two other winning candidates could be disqualified from the new Parliament, including one from Iraqiya.

The new potential disqualifications — and new appeals by two candidates who lost their seats in a partial recount completed last week — added more obstacles to the certification of the elections and the formation of a new government.

Referring to Mr. Hamid’s death, Haidar al-Mulla, a spokesman for Mr. Allawi’s alliance, said, “The security lapse is a very dangerous indication of what is happening in the absence of legislative authority.” He did not blame anyone for the killing, but he accused those raising challenges to the results — Mr. Maliki’s coalition, by inference — of delaying the seating of Parliament and the formation of a new government.

Atheel al-Najafi, the governor of Nineveh Province, complained that the Interior Ministry had denied police protection to the new Parliament members, like Mr. Hamid. Mr. Najafi, allied with Mr. Allawi, said it was premature to say who was responsible, but he added, “Several parties want to strike our list.”

It was not clear if Mr. Hamid’s killing was linked to his political victory. Mosul is one of Iraq’s most violent cities.

Only hours before Mr. Hamid’s death, an American soldier was killed in northern Iraq, the American military announced, without providing any details.

Mr. Hamid’s cousin, Mahmoud al-Qaidi, said two men approached Mr. Hamid’s office next to his home at 7:45 p.m. and joined a meeting in progress with six others. After a few minutes, they drew pistols and fired, hitting Mr. Hamid with seven bullets, the cousin said.

One gunman was reported arrested.

Under Iraq’s election law, Mr. Hamid will be replaced in the new Parliament by another candidate from his electoral bloc, officials said.

The candidates facing disqualification would also be replaced by members of their parties, meaning the preliminary results of the vote on March 7 have remained more or less the same, despite a flurry of legal challenges.

It was not clear why the latest efforts to disqualify newly elected lawmakers were undertaken at what seemed to be the end of the certification process. While Mr. Maliki’s critics have been quick to accuse him of using every means in his quest to remain in office, the circumstances appeared to reflect the convoluted bureaucracy of Iraq.

One of two winning candidates, Furat Muhsin Said, faces disqualification on the grounds that he continues to serve as a major general in Iraq’s Army, even though election law forbids him to do so. In an interview, General Said said he had offered his resignation to the defense minister, but that he had not apparently done so formally, according to election officials.

He won a seat on the election list of a predominantly Shiite bloc, the Iraqi National Alliance, which is now allied with Mr. Maliki but is objecting to his return for a second term as prime minister.

The other candidate facing disqualification, Abdulla Hassan Rashid al-Jibouri, belongs to Mr. Allawi’s coalition and received the highest number of votes in Diyala Province. The Interior Ministry recently informed the election commission that Mr. Jibouri should be disqualified because he had a criminal record, said an election commissioner, Sardar Abdul Karim.

Mr. Jibouri was the region’s governor before fleeing Iraq in 2005. He returned in 2009. Rasim Ismail, an aide, said Mr. Jibouri had been convicted in absentia on charges of fraud dating to his tenure as governor. After the election, Mr. Jibouri again left the country and is now in London, Mr. Ismail said.