Mike Pflanz: Shadow of Somali al-Shabaab looms over east Africa

The World Cup bombings in Kampala have increased fears that Somalia's al-Qaeda-linked Islamists are poised to carry through on their long-voiced threat to export their jihad outside the borders of their anarchic homeland.

The co-ordinated blasts at two venues popular with foreigners where hundreds had gathered to watch the finale of Africa's first World Cup killed 76 people.

Within 24 hours, from its stronghold in Somalia's bullet-scarred capital, Islamist group al-Shabaab was praising the attacks and claiming it carried them out.

"We were aware that they had been threatening this, but still it came as a horrific surprise to us," said Alfred Mutua, spokesman for the Kenyan government.

Neighbouring states, especially Ethiopia and Kenya, immediately ramped up security on their long and difficult to police borders with Somalia.

Kenya and Tanzania have been targets of radical Islamic violence launched from Somalia in the past. Al-Qaeda bombed the US embassies in Nairobi and Tanzania in 1998, killing more than 220 people.

In 2002, another al-Qaeda suicide attack on a Kenyan beach hotel popular with Israelis killed 13 people. Later that day, other members of the same cell tried to shoot down a Tel Aviv-bound passenger jet as it left Kenya's Mombasa airport.

So intelligence services are now on what Mr Mutua called "the highest possible level of alert".

But, as diplomats and security services privately warn, it is almost impossible for any state in the region entirely to protect its citizens against the danger of similar attacks in the near future.

Al-Shabaab - meaning The Youth in Arabic - emerged as the armed enforcers of the Islamist Islamic Courts Union, which controlled Somalia during 2006 and began firmly implementing strict sharia law.

It was ousted after Somalia's arch-enemy Ethiopia invaded, with western backing, and installed a transitional government in Mogadishu.

But the rump of the Courts Union, the hardline and most fundamental of its leaders, regrouped in the southern port of Kismayo and became al-Shabaab, bent on retaking control and imposing even stricter Islamic law.

Within months, foreign fighters blooded in Afghanistan, Pakistan and Chechnya began to arrive, drawn by al-Shabaab's call for men to mount a jihad against Ethiopia and the West. A handful have travelled from Britain, northern Europe and the US.

Today, the organisation has almost succeeded. It rules almost all of southern and central Somalia, and all but a few roads of the capital, Mogadishu.

All that blocks their route to total control is a force of 6,100 African Union peacekeepers, from Uganda and Burundi, providing the muscle for Somalia's powerless, western-backed government.

Threats of violence against both countries have flowed from Mogadishu's mosques for months, but there was international scepticism that the organisation had the capabilities to strike outside its borders.

"Obviously it's very worrying that al-Shabaab are now acting outside of Somalia," said Roger Middleton, Somalia expert at the Chatham House think-tank in London.

"But you'd need more evidence than these attacks to draw the conclusion that there is a network of their people already established in the region."

And it is wrong to think of al-Shabaab as a unified Islamist movement bent on internationalising its conflict across East Africa.

A sizeable majority of field commanders and footsoldiers are fighting for a nationalist agenda for Somalia alone, and have few offensive goals beyond that.

There is, many analysts have pointed out, general disgust among the Somali community at suicide bombings and the mechanisms of jihad imported from the wider al-Qaeda network.

"This could backfire on Shabaab, at least in Somalia, it will widen rifts at the top which are already getting wider by the day," said a British diplomat in Nairobi who covers Somalia.

"The problem is the money, from outside Somalia, will go to those with the internationalist agenda, and you don't need the backing of all of al-Shabaab to carry out something like Kampala."