Bassam Kuba, Iraqi undersecretary of foreign affairs, was shot dead outside his Baghdad home on Saturday as he left for work.
Kuba had just returned from New York where he was part of an Iraqi mission to the United Nations.
He was the first national official to be assassinated since the country's new transitional government was unveiled less than two weeks ago.
Details of his killing were still unclear said Thamir al-Aadhami, spokesman for the Iraqi Foreign Ministry.
"We heard that assailants opened fire on Bassam while he was driving his car near Assaf mosque," in the Aadamiya neighbourhood of Baghdad on Saturday, al-Aadhami told Aljazeera.
Kuba was taken to the Numan hospital where he died of his wounds.
Kurdish cleric assasinated
A Kurdish Sunni religious leader was also shot and killed on Saturday by assailants who attacked his home in Kirkuk, in the first such attack in the northern Iraq city.
Kuba's car was found riddled with
bullet holes outside his home
"Shaikh Iyad Kurshid Abd al-Razzak... was killed by shots from assailants which had entered his house in the Kurdish neighbourhood of Rahimawa," police Colonel Adil Ibrahim told AFP.
Razzak, 37, was an imam at al-Maza al-Thaniya mosque, and was known for defending the rights of Kurds in this oil-rich city.
This was the first attack on a Kurdish Sunni religious leader, said Ibrahim.
Meanwhile, a Lebanese and two Iraqi employees of a foreign company who had earlier been reported missing were found with their throats cut on a road near Falluja, a Lebanese diplomat said.
"Husayn Ali Alyan, from south Lebanon, and two Iraqis working for a telecommunications company disappeared on Thursday in the area around Falluja," said charge d'affaires Hassan Hijazi.
On the other hand, seven Turkish construction workers kidnapped two days ago in the same area were released and were on their way home, the Turkish embassy in Baghdad said.