By Tarik Kafala BBC News Online

A recent suicide attack and the killing of seven civilians at a coalition checkpoint in Iraq have brought into question the procedures and techniques used to run checkpoints.

For coalition forces, there are obvious security concerns.

Military checkpoints are used all over the world

If suicide attacks become a regular phenomenon, the whole issue of managing relations between US and UK soldiers and Iraqi civilians becomes much more difficult - and the soldiers manning the checkpoints much more nervous.

A BBC correspondent with US forces in Iraq, Gavin Hewitt, says the unit involved in the killing of seven civilians was the same unit that suffered four deaths at the hands of a suicide bomber on Sunday.

Political concerns are also important in this equation.

With the US and UK trying to win over the Iraqi population and to convince them that coalition forces can provide security and humanitarian aid, the handling of checkpoints is crucial.

Stop and search

The standard procedure at checkpoints is currently to stop and search all people and vehicles that want to pass through a checkpoint.

US soldiers are told to fire warning shots if a car fails to stop at a checkpoint.

US military officials say that in Monday's shooting at a checkpoint near Najaf in southern Iraq, soldiers fired shots over the car and then at its engine.

Aftermath of suicide attack at a checkpoint that killed four US soldiers near Najaf

When it failed to stop, they fired into the passenger cabin.

The Washington Post reports that warning shots were not fired in good time to halt the car.

The newspaper's reporter quotes the commander at the checkpoint saying to soldiers under his command: "You killed a family because you didn't fire a warning shot soon enough."

Rules of engagement

Each conflict tends to have or develop its own rules of engagement.

For the current war, military analysts say, the Pentagon has drafted guidelines that provide US soldiers with greater latitude to use force, but also greater obligations to take care of civilians than in previous conflicts. The written guidelines are classified.

A BBC correspondent at Central Command in Qatar, Paul Adams, says there is no indication that these rules of engagement are likely to be changed.

None of the current procedures at checkpoints specifically guard against suicide attackers - something that might well contribute to the nervousness of soldiers at checkpoints and increase the likelihood of incidents such as Monday's shooting.

Our correspondent says that while insisting that the correct procedures were followed in Monday's incident, more "aggressive" checkpoint procedures may be adopted.

Theses might include the use of barbed wire and barriers to stop cars at some distance from checkpoints and the soldiers manning them.

Israeli lessons

Military checkpoints are widely used all over the world and in conflict areas they are traditionally a point of tension.

Built-up checkpoints can feel like the infrastructure of occupation - something the coalition forces may want to avoid

The particular circumstances faced by coalition forces in Iraq, specifically the threat from suicide attacks, are comparable to the problems faced by Israeli forces.

Israeli checkpoints, even those in the occupied territories often take on the look and atmosphere of permanent international border crossings.

High fencing, large concrete blocks and watchtowers are standard at some of the bigger checkpoints run by the Israeli Defence Force.

Concrete slabs arranged in a zigzag pattern channel cars and force them to slow down to a crawl.

Cars are forced to stop and are approached by soldiers only when they are ready.

Watchtowers and observation posts allow Israeli soldiers to take a long and close look at the car and passengers trying to get through the checkpoint.

The Israeli authorities also carry out detailed ID checks and keep tight control on travel permits.

Signs of occupation

Of course Israeli checkpoints are one of the main manifestations of the Israeli occupations of large parts of Palestinian territory.

For Palestinians, the hours needed to get through checkpoints and the feeling of their lives being circumscribed are a source of tension and humiliation.

Checkpoints were also the scene of many of the clashes in the early stages of the current intifada.

Coalition forces may not want to build up their checkpoints and allow the impression to be created that they intend to be in Iraq for a long period of time.

Whether the US and UK want to commit resources to establishing well appointed checkpoints is also debatable.