The U.N. Assistance Mission in Iraq said 712 people were killed and 1,633 were injured in acts of terrorism and violence, CNN reported. Civilians who died or were injured numbered 595 and 1,438, respectively, the non-governmental organization said.
The most deaths -- 697 -- occurred in Baghdad.
April's death toll was the highest since June 2008, the U.N. mission said.
"The country is at a crossroads," said Martin Kobler, U.N. special representative in Iraq.
Some Iraqi and international leaders have expressed worry that tensions between Sunnis and Shiites could escalate into a full-blown sectarian war, CNN said.
Last month, the International Crisis Group said the "failure to integrate Sunni Arabs into a genuinely representative political system in Baghdad risks turning Iraq's domestic crisis into a broader regional struggle."
"The most urgent task today is to tamp down the flames, and the burden for this lies above all with the government," the think tank based in Belgium said in a report.