Shiite and Sunni Muslim preachers in Baghdad's mosques exhorted followers Friday to vote for their respective sects' blocs in next Thursday's fractious national elections, saying that checking the right ballot box was a religious duty.

A leading Shiite figure cited Koranic chapter and verse to claim divine endorsement for the current governing alliance, and normally more restrained Sunni clerics made similar assertions about opposition candidates. The linkage of religion and politics underscored the intensity of competition for seats in Iraq's first permanent government since the fall of Saddam Hussein. It also highlighted the surge of religious-based politics in Iraq, which was one of the Arab world's most secular countries during the first decades of Hussein's rule.

In Baghdad, text messages sent out on cell phones in recent days have pointed to occurrences of the number five -- the five tenets of Islam, for example -- in the Koran as evidence of preordained support for the ruling Shiite coalition, which was arbitrarily assigned the number 555 on the ballot.

"God is great!" worshipers in one of Baghdad's leading Shiite mosques cried at Friday prayers. "Allegiance to the heroes of the 555 List!" Their prayer leader, Jalal Sagheer, told them, "Remember that the number 555 corresponds to verse number 61 in the Koran'' -- a passage referring to the revelation of divine intent.

"Go out on election day and vote for the list most fit to represent you, the one that can deliver, bearing in mind that failure to do so means placing the fate of our security in the hands of others, which will lead to bloodshed," said Sagheer, a member of Iraq's National Assembly, reflecting the fear among both Shiites and Sunnis that power for one sect will mean persecution for the other.

Across town at the Um al-Qura mosque, Ali Zand, a Sunni cleric from the Association of Muslim Scholars, said: "December 15th is a landmark date. It is a decisive battle that will determine our future."

"If you give your vote to the wrong people, then the occupation will continue, and the country will be lost," Zand warned in a sermon quoted by the Associated Press. "Participation in the elections is a must, and it is a religious duty."

At another Sunni mosque, in northern Baghdad, Ahmed Hassan Taha used Friday prayers to ask insurgents to release four Western peace activists and humanitarian workers, including one American, kidnapped two weeks ago.

An Islamic group claiming to hold them has threatened to execute all four on Saturday unless the United States and Iraq free all prisoners here. Two other Westerners were also kidnapped recently, and an Islamic group claimed Thursday to have executed one of them, an American contractor.

Iraq's parliamentary elections will result in the country's first full-term, four-year government. Leaders emerging from Thursday's vote will oversee completion of a new constitution that could carve up Iraq's oil revenue; assumption of power from the U.S. military as the country's dominant security force; and a decision on splitting Iraq into two, three or more potentially highly independent, faction-based regions.

The elections, Iraq's third since the United States overthrew Hussein in 2003, have been characterized by slicker campaigning and dirtier politics. Rival Shiite militias shut down much of Baghdad last week for political marches.

On Thursday, U.S. Ambassador Zalmay Khalilzad cited attacks on campaign workers, political officers and candidates in Mosul, Basra, Baghdad and Najaf, where the offices of the leading secular candidate, Ayad Allawi, were rocketed. Khalilzad also alluded to events in the northern Kurdish city of Dahuk, where attackers burned the offices of an Islamic party that had broken away from the main Kurdish coalition. Four party officials were killed.

"These actions are assaults on democracy and attempts to deny Iraqis the freedom to vote their conscience," Khalilzad said in a statement. He also denounced what he said were attempts to buy votes but did not elaborate.

While competition among factions has been intense, and occasionally violent, coalition-building will be the theme for the post-election period, according to a Western official who spoke to reporters in Baghdad on Friday. The Shiite alliance now in power is not expected to win a majority of seats and will probably have to seek allies to form a new government, said the official, who spoke on condition of anonymity.

Special correspondent K.I. Ibrahim in Baghdad contributed to this report.