In west Baghdad's Omar al-Khattab mosque, a Sunni preacher assails his Shia compatriots for failing to come to the aid of the besieged city of Falluja.
?Those of the black turbans? Iraq's Shia clergy ?are but traitors and agents of America. It is they who have provoked the Amer-icans to attack the Sunni, whom they call extremists and terrorists,? Sheikh Ahmed al-Kubaisi told his congregation last Friday.
Mr Kubaisi's sermon is typical of many Sunni mosques across the country, where preachers are delivering fiery attacks on the Shia clergy who, they say, have ?sold out? Islam. In the aftermath of the Falluja battle, the insurgency has never been more divided along sectarian lines: guerrilla groups are overwhelming made up of Sunni Arabs, thought to make up about 20 per cent of the population, while most of the majority Shia and the minority Kurds support the interim government.
Both Sunni and Shia militants had put aside differences and found common cause back in April, when radical Shia preacher Moqtada al-Sadr took up arms against the US during the first siege of Falluja, which ended with insurgents in control of the town. During that campaign Shia mosques launched relief drives to aid Falluja and delegations from each sect visited the other's mosques with messages of solidarity.
However, Mr Sadr's followers have since laid down their weapons, and while he and several other Shia clerics have harshly condemned the Falluja offensive, more establishment clerics such as Grand Ayatollah Ali al-Sistani have remained silent on the assault; some have even supported it. The Sunni clerical establishment is particularly incensed by an appearance by Shia cleric Iyad Jamal al-Din on al-Arabiya satellite television, in which he praised the assault on the ?dens of terrorists and Saddam's supporters who know only violence in Falluja?.
The Sunni clergy feel particularly bitter because they denounced August's siege of the Shia holy city of Najaf.
?When Najaf was besieged we went to the Shia clerics and aided them with all our powers we have,? says Sheikh Abd al-Aziz al-Dulaimi, a prominent Sunni preacher. ?We won't forget the weak stance of the Shia [during] the aggression against Falluja … The Falluja crisis revealed the poisonous nature of the Shia.?
The Shia, however, continue to carry historical grievances against the Sunni, who dominated Iraqi politics for most of the last century and whom they blame for their terrible repression under Saddam Hussein. They also allege that Sunni groups are behind the assassination of Shia clergymen and dozens of others passing through the Sunni enclave of Latifiya south of Baghdad, which lies astride the route between the Shia holy cities of Najaf and Karbala and Baghdad.
One Karbala human rights group, al-Fiqar, estimates that 134 Shia have been murdered by ultra-puritan Sunni passing through the town, and virtually every leading Shia religious movement has a ?martyr? from this route.
Such murders and ambushes, a string of which were reported in August and September, have significantly reduced sympathy among Iraqi Shia for the Sunni insurgency.