BAGHDAD &

Gunmen from a messianic Shiite cult attacked police and worshippers preparing Friday for a major Shiite holiday, prompting fierce clashes that left at least 15 people dead a year after the group plotted a similar attack, authorities said.




Carrying yellow flags or wearing yellow headbands to show their allegiance to the Soldiers of Heaven cult, the gunmen attacked in Basra and Nasiriyah. Last year, U.S. and Iraqi troops battled cult followers in fields outside the holy city of Najaf after determining that its members planned to disguise themselves as pilgrims and kill leading clerics.




Authorities clamped a curfew on the two cities and security intensified in Najaf as more than a week of Ashoura observances were scheduled to climax Friday night through midday Saturday.




Iraqi officials have stepped up security across much of the country to protect the Shiite processions for the holiday period, which commemorates the death of Imam Hussein, one of the Shiites' most revered saints. In Baghdad, a 48-hour ban on heavy vehicles went into effect.




Pilgrims poured into the Shiite holy city of Karbala, home to the tomb of Hussein, the Prophet Muhammad's grandson who was killed during a seventh century battle in the area.




People lined up to be searched at the entrance of the twin shrines of Hussein and his brother Abbas. Tents providing tea, milk, food and first aid filled the streets outside.




Signaling continued political discord, a powerful Shiite politician accused the Iraqi government and legislators of allowing "personal whims" to delay national unity, addressing thousands of worshippers who rallied Friday in Baghdad to commemorate the death of one of the most revered Shiite saints.




The criticism in Baghdad by Abdul-Aziz al-Hakim, the head of parliament's largest Shiite political bloc, was among the strongest to date.




The intra-Shiite violence comes as a series of bombings that bear the hallmarks of Sunni militants in recent weeks have raised concerns about the sustainability of security gains made over the past six months.




The Soldiers of Heaven cult gained national attention last year when U.S. and Iraqi troops battled its members after uncovering the group's plot to kill as many leading clerics as possible in a bid to prompt the return of the Hidden Imam.




The "Hidden Imam" is a descendant of the Prophet Muhammad who disappeared as a child in the ninth century and Shiites believe that he will return one day to bring justice to each.




Most of those killed and wounded in Friday's clashes were police in Nasiriyah, a predominantly Shiite city some 200 miles southeast of Baghdad.




Street battles also broke out in Basra, another Shiite city 340 miles southeast of Baghdad.




Police said two officers died and four others were wounded in the fighting, which started after armed men attacked police and Shiites observing Ashoura. A mosque belonging to the cult also was burned by police after they were fired upon by people hiding inside, authorities said.




Basra police chief, Maj. Gen. Abdul-Jalil Khalaf, said later that the leader of the group in Basra, whom he identified as Abu Mustafa al-Ansari, was killed along with two other attackers.




"These terrorist groups have opened fire randomly on citizens and Shiite mourners and we are about to eliminate or arrest them," Gov. Mohammed al-Waili said. Police said 21 members of the group were detained.




British forces handed over control of Basra, home to much of Iraq's oil riches, to the Iraqis late last year, saying the security situation had improved.




Critics have accused Prime Minister Nouri al-Maliki's Shiite-led government of failing to take advantage of the nationwide decline in violence to embrace minority Sunnis and make progress on the political front.




Al-Hakim often has suggested he is displeased with the performance of the nearly 19-month-old al-Maliki government, of which the politician's Supreme Islamic Iraqi Council, or SIIC, is a major partner.




Speaking behind bulletproof glass, al-Hakim called on the government and parliament to pass stalled legislation on provincial elections and the distribution of Iraq's oil wealth, which are seen as vital to bringing Sunnis into the political process and stemming support for the insurgency.




"We are keen to form a national unity government despite the fact that election results allowed us to form a government that does not carry the characteristics of a national unity," al-Hakim said. "What is regrettable is that the national reconciliation process has been subjected to personal whims."




He also criticized government institutions of accepting "corruption and bribes" and called for mechanisms that would "prevent the blackmail of the people."




Al-Hakim, who was diagnosed with cancer last year but has been in relatively good health after chemotherapy in Iran, spoke before a sea of thousands who raised Iraqi and Shiite religious flags while chanting "We will never forget al-Hussein" and "We are the followers al-Hakim and (Grand Ayatollah Ali) al-Sistani."




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Associated Press writer Sameer N. Yacoub contributed to this report.