The US-led occupation is facing massive resistance almost everywhere in Iraq -- most recently a Chinook helicopter was shot down south of Falluja on November 2, killing 16 US soldiers, and rocket-fire caused the US forces to retreat from their Baghdad headquarters in the al-Rasheed Hotel on October 26.

But despite the increasing incidence of violent resistance within the "Sunni Triangle" in central Iraq, in many ways the most troubling news for the occupation forces comes from the holy city of Najaf some 100 miles south of Baghdad and has to do with the machinations of Moqtada al-Sadr -- a fiery young cleric who is attracting increasing support for his outspoken opposition to the US-led occupation.

Moqtada al-Sadr has a huge following among young Shiites -- especially the poor -- on the streets of Sadr City in Baghdad. His power base is a network of charitable institutions founded by his father and he has his headquarters in the holy city of Najaf in the Shiite heartland south of Baghdad.

He is the youngest son of Muhammad Sadiq Sadr, who was a senior Shiite cleric who died in a car crash in 1999, widely thought to have been an assassination ordered by Saddam Hussein. The teeming slum area of Baghdad which is home to 2 million impoverished Shiites and used to be called Saddam City has been renamed Sadr City by its inhabitants in honour of the elder Sadr.

In July, more than 10,000 demonstrators rallied in Najaf in support of Moqtada al-Sadr, and in August, he rallied 30,000 demonstrators to a fierce speech denouncing the US-led occupation. His popularity and influence has only increased since then.

In October, al-Sadr denounced the formation of the US-sponsored governing council and announced that he would form a competing shadow government to challenge the authority of the governing council. "Any Shiite who cooperates with occupation forces is not a Shiite," he declared at a news conference in early October.

Most ominously for the US-led occupation, soon after this declaration two US soldiers were killed in a gunfight with members of al-Sadr's al-Mahdi militia in Sadr City.

The occupation authorities arrested 12 of al-Sadr's supporters in Sadr City on October 16 and last week 32 al-Sadr supporters were arrested in Karbala over the killing of 3 US soldiers and 2 Iraqis in a shoot-out between US forces and forces thought to be under the command of another radical cleric who has been linked to al-Sadr -- Ayatollah Mahmoud al-Hassani.

The one positive for the US in all of this is that al-Sadr is not without his own detractors within the Shiite religious establishment in southern Iraq. Most Iraqi Shiites look first for leadership to one of the four grand ayatollahs of Najaf -- Mohammad Said al-Hakim, Ali al-Sistani, Mohammad Ishaq Fayadh, or Bashir al-Najafi. These four ayatollahs and their supporters consider the young al-Sadr a dangerous and opportunistic trouble-maker who is attempting to usurp their authority. He has been accused of complicity in the April killing of a moderate Shiite leader who had worked with the US and UK governments from exile and with the attempt on the life of Ayatollah al-Hakim in August.

However, the four grand ayatollahs are compromised in the eyes of many by what is seen as their acquiescence to the US-led occupation. The senior clerics and the former exile group, the Supreme Council for the Islamic Revolution in Iraq (SCIRI), which is headed by the brother of Ayatollah al-Hakim, supported the US-led war to oust Saddam Hussein and favour cooperation with the occupation forces.

As the situation in Iraq continues to deteriorate and Iraqis become more and more hostile to the US-led occupation, the established Shiite leadership runs the risk of being outflanked by al-Sadr and his more radical message. Given the contrast between their accommodation to the US-led occupation and al-Sadr's fiery denunciations, it is easy to understand why al-Sadr's popularity and influence continues to grow.

Another factor that sets al-Sadr apart from his four senior rivals for the hearts and minds of Iraq's Shiite majority is that he makes no secret of his political ambitions or his vision of Iraq as a Shiite theocracy. In contrast, the Shiite establishment has been unable to articulate any kind of compelling vision for post-occupation Iraq and the grand ayatollahs seem hesitant to assume the mantle of political leadership.

The present turmoil raging in the Sunni Triangle should not blind the US to the trouble brewing in the Shiite heartland south of Baghdad. The power vacuum into which al-Sadr has stepped is exactly the type of problem that critics of the war warned of and that the US has been unable to contain. Iraq's continuing descent into chaos will only serve to empower the most radical of alternatives such as al-Sadr, and within this unrest the US appears to have no coherent plan that speaks to the aspirations of Iraq's Shiite majority or for dealing with the sky-rocketing popularity of the one figure who does.

Zafar Sobhan is an Assistant Editor of The Daily Star