The impact of the Iraq war is now being felt across Middle East

So now they have struck in Qatar. Nice, friendly, liberal Doha, with its massive US air base and its spiky, argumentative al-Jazeera television, its modern shops and expatriate compounds and luxury hotels. Ever since al-Qa'ida urged its supporters to strike around the maritime Arab kingdoms of the Gulf, the princes and emirs have been waiting to find out who's first. Saturday's suicide bomber - and the killing of a Briton - gave them their answer.

So now they have struck in Qatar. Nice, friendly, liberal Doha, with its massive US air base and its spiky, argumentative al-Jazeera television, its modern shops and expatriate compounds and luxury hotels. Ever since al-Qa'ida urged its supporters to strike around the maritime Arab kingdoms of the Gulf, the princes and emirs have been waiting to find out who's first. Saturday's suicide bomber - and the killing of a Briton - gave them their answer.

The first indications were that the killer was an Egyptian called Omar Ahmed Abdullah Ali, for it was his car which exploded outside the Doha Players Theatre in the suburb of Farek Kelab. But there was no doubt about the seriousness of the original warning. "To the brothers of Qatar, Bahrain, Oman, the Emirates and to all the lions of jihad in the countries neighbouring Iraq, everyone of us has to attack what is available in his country of soldiers, vehicles and air bases of the crusaders and the oil allocated for them," it said.

The audiotape was made by Saleh al-Aoofi, a Saudi follower of Osama bin Laden who is credited as leading al-Qa'ida's operations in the Gulf.

America's largest air base is in Qatar. Bahrain is home base to the US fleet in the Gulf. American and British warships are regularly alongside in the emirate of Dubai. Oman has long been an ally of the US and Britain. And all have substantial expatriate populations. In Dubai, they used to say, it was difficult to find a citizen of the Emirates because of the vast population of Britons, French, Russians, Sri Lankans, Pakistanis and Indians. In the old days, you could ring the Omani defence ministry and, like as not, the phone would be answered by a lady from Godalming.

So the Iraqi insurgency is now, it seems, to embrace all these "safe" locations. The last time Qatar witnessed violence was the car bomb which killed the former Chechen rebel leader Zelimkhan Yandarbiyev - for whose murder two Russian agents are now languishing in jail. But the weekend's bombing was directed at a specifically Western target - albeit that a theatre hardly qualifies as an air base.

So safe was Qatar believed to be that the US imprisoned Saddam Hussein there. Indeed, his first wife, Sajida, and her children live in the emirate at the private invitation of Sheikh Mohamed bin Khalifa al-Thani. The Qatari interior ministry stated that the Egyptian was solely responsible for the explosion - which seems highly unlikely. It takes considerable sophistication to rig a car bomb, and those who prepare the vehicles are too valuable to their organisations to be sacrificed in an attack.

Sheikh Mohamed received the usual rash of phone calls from his opposite numbers in Kuwait, Bahrain and the Emirates. Compared with recent attacks in Saudi Arabia and Kuwait, Saturday's was small-scale.

Qatar's own population has long been friendly to foreigners even though these are increasingly military. There is also a large CIA base in the emirate and US special forces troops live in guarded compounds in residential areas of Doha.

The real purpose of the bombing, however, may have been economic. Al-Qa'ida's assaults on Saudi Arabia and Kuwait were almost certainly intended to raise the price of oil. Qatar exports gas. Iraq's oil exports have been interrupted by hundreds of insurgent attacks on its pipelines. The idea that "regime change" would bring new-found stability to the countries of the Gulf - another of President George Bush's excuses for the 2003 invasion - now appears to be a myth.

That this weekend marks the second anniversary of the invasion may have been in the bomber's mind. Certainly it coincided with attacks inside Iraq, including a suicide bombing in Mosul, the killing of another US soldier near Tikrit and a roadside bomb near Basra. The crisis in Lebanon provoked by the former premier Rafik Hariri's murder has drawn attention away from Iraq even as the insurgency grows in strength.

The reality is that the Iraqi invasion now reverberates across the Middle East. Hariri was the leading proponent of a Syrian military withdrawal - which the US supports, primarily because it holds Damascus responsible for helping Iraqi insurgents. Lebanese officials have even claimed privately that Hariri's friendship with the Iraqi interim prime minister, Iyad Allawi - himself half-Lebanese - brought about his death, a suggestion which neither the Americans nor the UN takes seriously.

Now the smaller Arab nations of the Gulf await the next assault - which no amount of expatriates and foreign soldiers can protect from al-Qa'ida.