"The Shebab is an organisation that has a regional agenda. The very top leadership of the organisation see themselves as pursuing something above and beyond just a Somalia national agenda," said Nick Kay, the UN's special representative in Somalia.
"It has had the capability and intent to carry out attacks across the region for some time," Nick said, adding that this intent is "stronger now".
The Shebab has recently stepped up attacks against countries that contribute to the 22,000-strong, UN-backed African Union force deployed against them in Somalia since 2007.
The group also claimed responsibility for two raids earlier this month in a Kenyan tourist area which killed around 60 people.
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On Thursday, Shebab gunmen had attacked an African Union military base in central Somalia dressed in stolen government army uniforms, killing at least two soldiers from Djibouti, the AU said.
"It does require the countries of the region, with the support of the international community, to be much more joined up in their approach," Kay said today, calling for greater information-sharing and stronger border controls.
Somalia is due to put in place a new federal constitution in 2015 and hold elections in 2016, although the security situation could delay progress.
Chased out of Mogadishu in mid-2011, the Shebab have also abandoned key bastions in the country's border areas but retain control over vast swathes of Somalia's rural hinterland from which they carry out regular guerrilla attacks against government institutions and international forces.