Details of al-Haidri's death on Tuesday remain unclear.
Al-Haidri is the most senior Iraqi official to be assassinated in Baghdad since the head of the Governing Council was killed by a bomb in May last year.
He had survived a previous assassination attempt in September.
Armed fighters have repeatedly targeted Iraqi officials as well as the country's fledgling security forces as part of a fierce effort to destabilise the US-backed interim government.
Also on Tuesday, a truck bomb exploded at a police post near an entrance to the fortified Green Zone complex in Baghdad, killing at least 13 people and wounding at least 28.
Speaking to Aljazeera, Iraqi journalist Ziyad al-Samarrai said a very loud explosion rocked Baghdad at 8.50am (0550 GMT).
Bombers have targeted the
Green Zone on many occasions
The journalist said the explosion targeted the headquarters of the special Iraqi forces in al-Qadisiya neighbourhood in Baghdad.
Ambulances rushed to the explosion site, while Iraqi police and US forces cordoned off the area, he said, adding that columns of smoke were seen rising from the site and some nearby houses were also damaged in the explosion.
The Green Zone is a sprawling complex housing the interim Iraqi government and the US and British embassies. Bombers have attacked entrances to the complex several times.
The blast followed at least two car bomb attacks in the capital on Monday. One of the attacks killed two policemen and a civilian near interim Prime Minister Iyad Allawi's party headquarters.
Three British nationals were also killed in a Baghdad explosion on Monday, the British Foreign Office said.
Separately, a US marine was killed in action in al-Anbar province, west of Baghdad, on Tuesday, the US military said, giving no further details.
Al-Anbar province includes the cities of Ramadi and Falluja, where US forces launched a major assault in November.
Since the invasion to oust Saddam Hussein in March last year, at least 1049 US military and Pentagon personnel have been killed in action in Iraq.
Including non-combat deaths, the toll is now at least 1334.
Later in the day, a Turkish oil tanker was burnt by unidentified fighters in central Mosul city, Aljazeera learned. The driver's fate is still unknown.