Baghdad - Iraq's deadliest single bombing in 13 years of war has turned the Baghdad district where it took place into the centrepiece in an increasingly bitter rivalry between the country's prime minister and its Iranian-backed Shi'ite militias eager to hold sway over the city's most diverse and prosperous area.Karada, a commercial hub on the east bank of the Tigris River, long had a reputation as one of Baghdad's most diverse neighbourhoods. Though it has a Shi'ite majority, it boasts large Sunni Muslim and Christian communities and has the largest number of churches in a single Baghdad neighbourhood. It was home to much of Iraq's once large Jewish community, which mostly left the country by the 1950s.Since the US-led invasion in 2003, it has been hit by seemingly endless suicide attacks, roadside bombs and even rocket shelling. But it was spared the sectarian bloodletting and cleansing that tore the rest of Iraq's capital apart and is perhaps the only neighbourhood left in the city where Sunnis and Shiites live side-by-side.But the July 3 suicide bombing that killed nearly 300 and wounded 200 others may have been one attack too many.'This one is different'The blast, for which the Islamic State group claimed responsibility, set fires that ripped through two shopping malls, raising the death toll and horror of the attack. Some of Karada's deeply shaken residents are asking Shi'ite militias for protection."This one is different," said Haidar Hadi, a resident who works at a Karada women's clothing store. "Too many people were killed and it all happened when people were fed up with security conditions," said the 26-year-old who, like his co-workers, wore mourning black.Iranian-backed Shi'ite militias, who style themselves as Iraq's strongest protectors against militants, are stepping in, trying to gain influence in the district. It is part of a wider competition for political power between them and Prime Minister Haider al-Abadi, who has tried to limit the militias' role. In the case of Karada, it could jeopardise the district's inclusive character, given the hatred and fear among Sunnis of the militias.Hours after the bombing, al-Abadi visited Karada, only to be met by some residents shouting insults at him. He had to rush away in his convoy as residents hurled water bottles, rocks and shoes at it, yelling, "thieves" and "pickpockets", a reference to allegations of widespread government corruption.The next day, two of the most powerful Shi'ite militia leaders, Hadi al-Amiri and Qais al-Khazali, both harsh critics of al-Abadi, toured the site. Some residents, overwhelmed with emotion, approached the two, pleading for help to protect Karada and avenge the victims.Muqtada al-Sadr, a radical Shi'ite cleric whose followers in April stormed Baghdad's heavily fortified "Green Zone" that houses parliament and government offices, visited the bombing site on Tuesday."The site must be kept as a monument to the people's suffering from corruption and terror," said al-Sadr, whose Saraya al-Salam, or Peace Brigades, militia is among Iraq's largest.Al-Amiri called on the government to hang convicted IS militants on death row in the streets of Karada as retribution.Al-Khazali vowed to avenge the bombing and demanded the militias be allowed to "cleanse" the environs of Baghdad. "Now that the state's security and intelligence institutions have failed to carry out their duties ... the Popular Mobilization [the formal name of the Shi'ite militias] must be involved in the security file," he said.Al-Abadi responded, over the weekend, saying no one would be allowed to make political gains out of the tragedy, and no one except security forces would be allowed to carry arms inside the city.War against ISISSome Iranian-backed militias have offices in Karada, but they've had little influence among its Shi'ite community. Most Shi'ites in the district are followers of Iraq's top religious leader, Grand Ayatollah Ali al-Sistani, a moderate cleric who has repeatedly been critical of militiamen over their abuse of Sunni civilians while fighting the Islamic State north and west of Baghdad.Karadah's residents have tended to join volunteer brigades loyal to al-Sistani in response to his June 2014 call for a jihad, or holy war, against ISIS after it blitzed across much of Iraq. While militiamen often operate as unofficial security forces in other Shi'ite-dominated districts, they are absent from Karada.Al-Sistani's representative declared in a Friday sermon that it was no longer possible to "show leniency to the corrupt and the losers at the expense of the blood and lives of citizens", a thinly veiled criticism of the prime minister for failing to make good on his calls to reform the government and shake up his security forces.The representative, Sheikh Ahmed al-Safy, also visited the bombings site and attended some of the funerals.Amid the mounting pressure after the bombing, al-Abadi sacked the capital's security chief and accepted the resignation of the interior minister, a veteran member of the Badr Brigade led by al-Amiri.Iraq's Shi'ite militias have grown in size and influence during the fight against ISIS. After much of the military and security forces melted away in the face of the ISIS blitz in 2014, the militias rallied to push the militants back from the outskirts of Baghdad. They have also grown in political ambition and become bolder in criticising al-Abadi.At the same time, they are accused of abuses of Sunnis in territory they retook from IS. And they have had friction with the military as it rebuilds and gains some successes of its own against the extremists.The militias are believed to be manoeuvring to become the main armed force in the capital, a city of around 7 million.'There is fear and horror in our hearts now'Currently, the army is in charge of security in Baghdad. But the Interior Ministry, which is known to be close to the militias, has long wanted to take that role from the military, the chairman of parliament's security and defence committee, Hakem al-Zamli, told The Associated Press."That could effectively mean the militias taking over in Baghdad," he said.Militiamen, meanwhile, are maintaining a daily presence at the site of the Karada bombing. The burned shells of the mall have turned into a makeshift shrine attracting thousands of visitors every day to commemorate the victims - and vent their frustration at the government's perceived failure to protect the city against ISIS.Unarmed but in combat fatigues, the militiamen take part in funerary processions at the site. The banners of several militias are hoisted over the shopping malls. On Sunday night, they organised and acted as pall bearers for a symbolic funeral for the dozens still unaccounted for a week after the blast."I doubt that Karada will ever return to what it was before the bombing," said survivor Majid Toamah, a 40-year-old store owner. He lay on his back on the floor in a relative's home with both legs in a cast, broken when he leaped 20m to the street below to escape the fire. "There is fear and horror in our hearts now.""There is so much hatred for Karada because it has all the goods anyone needs and is home to all sects and everyone loves everyone else."