By Frank Gardner BBC security correspondent

There are growing signs that US forces and civilians in Kuwait face a bigger threat than was previously recognised.

Following a fatal shootout on Failaka Island on 8 October, the Kuwaiti authorities have been rounding up dozens of friends and relatives of the two Kuwaitis who fired on US Marines.

Local security sources say the investigations are yielding some alarming results.

Jassem al-Hajeri was one of the two Kuwaitis killed

Maps, blueprints and details of schools and residences where Americans live have all been seized, according to the respected Kuwaiti paper, Al-Qabas.

US investigators suspect the two assailants were linked to Osama Bin Laden's al-Qaeda network and received training in Afghanistan.

Embarrassing

Their actions have been condemned by Kuwaiti officials and also by mainstream Islamic groups.

For them, this is all very embarrassing.

Kuwaitis may be privately critical of US policy towards Israel and the Palestinians.

But most of the country's 800,000-plus nationals recognise that there is only one thing stopping their country becoming the 19th province of Iraq - the huge US military presence on their soil.

Put simply, they want them to stay. But it is becoming increasingly clear that for a small minority of Kuwaiti extremists, their hatred of US policy overrides their national sense of self-preservation.

At the funeral of the two gunmen killed when US Marines returned fire, there were fiery statements about martyrdom, holy warriors, and the need to fight America.

Even before the shooting, a well-known university professor, Dr Abdullah Al-Nafisi, was interviewed saying that it was hard to "distinguish between what is American and what is Zionist".

A recent statement attributed to Osama Bin Laden, he said, was "historic" and "filled with religious honesty".

Even while Kuwaiti police were still rounding up suspects for Tuesday's shooting, another incident took place on a road leading towards Iraq.

US soldiers driving in their Humvee jeep saw a passenger in another vehicle pointing a gun at them.

The Americans opened fire, forcing the Kuwaiti vehicle off the road, but sped on themselves.

Alarming precedent

Compared to the massive conflagration that may erupt in the Gulf within months if America goes to war with Iraq, these events are miniscule.

The injured marine recovering in hospital

But for Washington, they have set an alarming precedent. If there was one Arab ally America feels it can rely on unequivocally, it is Kuwait.

It still can and it still will.

But not all the population shares its government's enthusiasm for this alliance.

From now on, Americans living and serving in Kuwait are going to need eyes in the back of their heads.