AT the end of a week which has seen an upsurge in violence with the deaths of around 100 Iraqis and coalition workers, Western intelligence services are divided in their responses to Abu Musab alZarqawi, the Jordanian-born terrorist who is reported to be the mastermind behind these recent attacks.

Is he a bogeyman who can be blamed for every violent incident, or, next to Osama bin Laden, is he the most dangerous threat to the emergence of a free and democratic Iraq?

When the Jordanian-born terrorist first became associated with the insurgency in Iraq, senior commanders tried their best not to demonise Zarqawi in order to quash Iraqi perceptions that he was a cross between Saladin and Robin Hood and would never be caught.

A typical put-down in US military circles was that "Zarqawi is like Elvis, he's everywhere". But following last week's spate of violence in Iraq, with all the incidents being linked to the terrorist leader's name, the coalition security forces are taking a more sanguine approach to the threats of violence which are linked to him.

In the week before the British general election is due to take place, senior officers in southern Iraq are taking seriously threats that their forces might be targeted in an attempt to push Iraq back on to the agenda.

Zarqawi has already called on his supporters to continue their attacks on "collaborators" - Iraqis who work for the coalition or who support the interim government and there are fears that the main thrust of the insurgency could move away from the area around Baghdad to the southern British-controlled sector in the south.

Although Zarqawi lacks a power base in this Shia area - his main influence is among former members of the Ba'ath Party in the Sunni Triangle - security officials are not discounting the possibility that an attempt will be made to mount a "spectacular" following a warning that "Britain will not escape Iraq without punishment".

A senior military source told the Sunday Herald that while British and multinational forces have secured and largely pacified the British area of responsibility, the insurgents still possess the capacity to surprise the coalition with a high-profile attack.

"Zarqawi has shown that he is well capable of marshalling his people and changing their role as the local situation changes, " he said.

"He has also learned from terrorist groups like the IRA and understands the importance of operating a tight cell structure. He supplies the funds, the intelligence and the weapons and as we are seeing there is a new sophistication to the insurgents' tactics. And like the IRA, he knows all about hitting the headlines at the right time - it wouldn't surprise me if he tried it on with us."

At the same time the officer insists that it is wrong to put too much emphasis on Zarqawi, in the same way that al-Qaeda is automatically associated with every terrorist outrage as if it is an international franchise. For a start, as is so often the case in this conflict, there is very little hard evidence about the man and his activities.

In recent briefings the CIA have even cast doubt on whether or not he lost a leg in Afghanistan in 2001 following a US missile strike on Taliban training camps.

The extent of his connection with bin Laden is also open to question and although his name has been associated with the worst outrages in Iraq it has proved impossible to track him down or penetrate his cell structure.

That failure to discover his whereabouts or to encourage his associates to defect or break ranks means that Zarqawi remains a shadowy figure who is also a handy fall-guy when things go wrong.

Coalition commanders have already conceded that the majority of the insurgents are not imported foreign fighters under Zarqawi's command but local men, many of whom were connected with the Ba'ath Party or served with elite military units such as Saddam Hussein's Republican Guard.

While it is true that the number of incidents against coalition forces and Iraqi targets has dropped since the January election, there has been a new intensity and complexity to the attacks that have taken place. In a daring suicide bomb attack against an official convoy last week the interim prime minister Iyad Allawi narrowly escaped being killed, a sign that the insurgents are now targeting highprofile figures, and at Haditha northwest of Baghdad 19 Iraqi National Guard soldiers were kidnapped by insurgents and then summarily executed in the local football stadium.

In other incidents a Bulgarian helicopter was shot down with the loss of 11 lives, 10 Iraqis were killed in Baghdad bus outside the Shia mosque at al-Subeih after prayers on Friday, and three Western workers were murdered in a Baghdad street.

These were barely reported in the West but the most chilling manifestation of the unrest came when 58 bodies were fished out of the River Tigris near al-Suwayra.

They were thought to be the remains of Shia hostages taken prisoner and then murdered after a stand-off with Sunnis in the town of Madain, but Yahia Said, an Iraqi expert at the London School of Economics, claims that the deaths might be "a tribal feud that ended acrimoniously".

The majority were men and had either been shot, beheaded or had had their throats cut.

Whatever the provenance of the killings they send the worrying message that the activities of the insurgents have become more daring and that long-running tribal or religious confrontations are in danger of spilling over into open conflict.

One report from al-Suwayra claims that tensions between the Sunni and Shia communities have been unusually high in recent weeks and that dead bodies have been turning up in the River Tigris since the end of February.

There have also been reports of Sunni militant activity as well as sightings of units from the Badr Brigade, a Shia militia with a history of fomenting communal violence.

On Friday Grand Ayatollah Ali al-Sistani urged his Shia followers to refrain from violence and to refuse to get involved in internecine confrontations but with violent incidents now a daily occurrence, further communal clashes now seem unavoidable.