Coalition forces and Iraqi police clashed with Shi'ite protesters near the city of Najaf, and hospital officials say at least 22 people were killed and scores injured in the fighting. Supporters of the radical Shiite cleric Muqtada al-Sadr have been staging protests in Shi'ite areas of central and southern Iraq for the past several days.
The demonstrations turned violent when Spanish-led troops and Iraqi police battled with Shi'ite marchers near a coalition base in the town of Kufa.
The protesters were furious about the U.S. decision to temporarily shut down a newspaper headed by Moqtada al-Sadr, an outspoken cleric known for his harsh criticism of America. U.S. officials closed the newspaper's offices on March 28. They said the paper was inciting violence against the coalition.
Many Shi'ites are also angry over the alleged detention of a top aide to the cleric, Mustafa al-Yacoubi, but Spanish troops in charge of security around Najaf insist they have not arrested him.
Shi'ite demonstrators shouting anti-American slogans also took to the streets in Baghdad. They gathered at the entrance to coalition headquarters and in the square where the statue of Saddam Hussein was toppled last year. Some chanted "Down America", "Down Israel", and burned U.S. flags.
U.N. special envoy Lakhdar Brahimi is scheduled to arrive Monday in Iraq to try to work out a compromise with Iraq's Shiite community over the political future of the country.
In early March, another influential Shi'ite cleric, Ayatollah Ali al-Sistani called Iraq's interim constitution an obstacle and said any transitional law must be approved by an elected national assembly.
The ayatollah warned that Iraq's Shi'ite majority will not cooperate with U.N. officials charged with overseeing the transfer of sovereignty unless they agree to abandon the document.
Meanwhile, U.S. officials announced that two Marines were killed during the weekend in separate clashes with Iraqi insurgents in the western province of Anbar. The province is also home to the predominantly Sunni Muslim city of Fallujah, where four American civilians were killed and their bodies mutilated by cheering Iraqi crowds last week.