The scale and sophistication of attacks are on the rise, worrying signs as Iraq's new leaders prepare to take power, said Annan on Thursday in his latest report to the Security Council about Iraq.
Earlier on Thursday, a bombing at a Shia mosque killed 47 people, and on 28 February, a car bomber killed 125 people, mostly Shia police and National Guard recruits.
Iraqis will expect security and living conditions to improve now that their elections are complete, Annan said.
But the government and multinational forces must tread carefully, he said. "Particular care should be taken by those responsible for ensuring security to see that their actions do not adversely affect the civilian population," Annan wrote in the report.
The rise in violence is troubling because many Iraqis and outsiders had expressed hope that the election would help reduce the fighting and were encouraged by the lull afterwards.
Annan reviewed UN actions over the past three months. His report praised the 30 January election, saying the vote offered a new opportunity for Iraqis to build a democratic country.
On Thursday, a blast at a Shia
mosque killed at least 47 people
The next step will be crafting a constitution. Annan said his special representative, Ashraf Qazi, was meeting Iraqis to promote dialogue as they go about drafting the constitution.
It is up to the new government to make sure the population feels it can participate in the country's reconstruction. Soon after the report was released on Thursday, Iraq's main Shia party and a Kurdish bloc said they reached a deal that sets the stage for a new government to be formed.
The deal between the clergy-backed United Iraqi Alliance and a Kurdish coalition will allow a new government to be named when the National Assembly opens next week.
Annan warned of the possibility of still more strife between Sunnis and Shia, saying it was crucial to seek reconciliation now rather than let simmering unrest boil over into a wider conflict.