A series of bombs exploded Wednesday across Iraq ahead of a major Shiite pilgrimage Saturday to commemorate the death of Imam Moussa al-Khadhim, grandson of the Prophet Mohammed.
Martin Kobler, U.N. special envoy to Iraq, described the scale of violence as "disturbing," adding he was "deeply shocked and utterly dismayed" by the attacks.
"I urgently appeal to the government to address the root causes of the violence and terrorism that are causing so much suffering and pain to the Iraqi people," he said in a statement.
Attacks last week left at least 18 people dead and more than 100 wounded following disputes between Sunni and Shiite endowment offices over control of the Askariya Shrine in Samarra. A 2006 bombing of the mosque pushed the country toward civil war.
The latest attack comes as pressure mounts on Iraqi Prime Minister Nouri al-Maliki. Critics accuse the two-term prime minister of monopolizing power.
British Minister for the Middle East Alistair Burt, in a statement, said the attacks, which targeted mainly Shiite pilgrims, were appalling.
"I urge all political blocs in Iraq to work together and focus on bringing security and stability to all of Iraq," he said.