Gunmen burst into a Baghdad office of a non-governmental organization on Monday and shot dead the five people inside, Iraqi police said.
The attackers planted a bomb in the entrance to the office which exploded when security forces arrived, killing or wounding some of them, local Sunni neighborhood guard chief Nabil al-Qaisi said.
No reason was immediately apparent for the attack in a predominantly Sunni area of the Iraqi capital. Police gave conflicting information about the NGO but local residents believed it was involved in distributing humanitarian aid.
Members of other aid groups operating in the area said no gunshots were heard, suggesting that silenced weapons were used.
Some police sources said four men and one woman were killed while Kaisi said the victims included three men and two women. Baghdad security spokesman Major General Qassim al-Moussawi said three people were killed.
Kaisi said the neighborhood was once a bastion of al-Qaida.
Anger is simmering in Iraq's once dominant Sunni community over efforts by an independent panel to ban around 500 candidates from a March 7 general election because of alleged links to Saddam Hussein's outlawed Baath party.
Many on the list are believed to be Sunni, triggering suspicions that the ban reflects an attempt by the Shiite Muslim-led government to sideline Sunnis in the vote.
One of the few whose name has been made public is prominent Sunni politician Saleh al-Mutlaq. But the list also includes Shiite Prime Minister Nuri al-Maliki's defense minister.
The raging sectarian war between Sunnis and majority Shiites unleashed by the 2003 U.S. invasion has largely subsided. But bomb attacks and assassinations remain a daily occurrence in much of the country.
Iraqi and U.S. officials say they expect attacks to increase ahead of the parliamentary election in March, which will be a test of Iraq's growing stability.
