An al-Shabab commander who was the target of a recent abortive US special forces raid in Somalia had spent time in the UK, the BBC has learned.
Abdukadir Mohamed Abdukadir, widely known as Ikrima, has been linked to alleged terror plots in Kenya.
Friends have told the BBC that he came to the UK in 2007 and spent time in London, before moving to Somalia the following year.
US Navy Seals failed in an attempt to capture him on 5 October.
The raid followed an attack on the Westgate shopping centre in Nairobi, Kenya, on 21 September that lasted four days and left at least 67 people dead.
Al-Shabab has claimed responsibility for the siege.
The BBC’s East Africa correspondent Gabriel Gatehouse said it was not clear what role, if any, Ikrima had played in that attack.
He is thought to be a recruiter of foreign fighters, and a key link between al-Shabab in Somalia, and al-Qaeda in the Arabian Peninsula, based in Yemen, our correspondent added.
In 2004 he travelled to Norway, where he unsuccessfully sought asylum.
The BBC has discovered that in early 2007 he came to Britain and spent time in London, before moving back to Somalia.
Leaked Kenyan intelligence documents have linked him to Samantha Lewthwaite – the British widow of one of the 7/7 suicide attackers on the London transport system in 2005.
An alleged plot to bomb targets in Kenya was foiled, police say, when they raided a number of addresses in Mombasa in December 2011.
Ms Lewthwaite slipped away, her whereabouts are unknown.
Our correspondent said the Kenyan authorities believe apprehending Ms Lewthwaite and Ikrima could help prevent future attacks similar to the one at Westgate.
Appeal for troops
Meanwhile, UN Secretary General Ban Ki-Moon has said an extra 4,500 troops are needed by the UN-backed African Union force (Amisom) fighting al-Shabab in Somalia.
Mr Ban said in a report to the UN Security Council that recent military advances against al-Shabab could be reversed and there was a danger of more Westgate-style attacks if the 18,000-strong force was not bolstered.
Al-Shabab said it had staged the attack on Westgate in response to Kenya’s army joining Amisom and carrying out operations on Somali territory.
The UN chief said that in addition to a troop surge, which would have to be paid for by richer UN member states, the African force also needed military attack helicopters.
He appealed to both African and non-African countries to supply these.
The BBC’s international development correspondent Mark Doyle said the African Union had requested a boost of more than 6,000 troops, so concern had been expressed by African diplomats at the lower figure recommended by Mr Ban.
In the past two years, Amisom has made significant advances against al-Shabab, pushing their main armed units out of several cities including the capital, Mogadishu, and the key southern port of Kismayo.
But the militants still control many smaller towns and large rural areas of southern Somalia.