The 23-year-old was
named as Hassan Abdi Dhuhulow, who the BBC said is suspected of helping
to plan and carry out the attack on the upmarket Westgate mall.
Dhuhulow was born in Somalia, but he and his family moved to
Norway as refugees in 1999, according to relatives who spoke to the BBC
from the Norwegian town of Larvik, 120 kilometres (75 miles) south of
the capital Oslo.
The BBC quoted one of Dhuhulow's former neighbours Morten Henriksen, who described the young man.
"He
was pretty extreme, didn't like life in Norway... got into trouble,
fights, his father was worried," Henriksen told the BBC, speaking of
Dhuhulow as a teenager.
Last week Norway's PST
intelligence agency said it had launched a probe after it obtained
information about the possible involvement of a Norwegian of Somali
origin in both planning and carrying out the attack.
Norwegian investigators have been sent to Nairobi to work with their Kenyan counterparts, Norway's PST said.
Witnesses
in the mall described how the fighters stormed the complex around
midday on September 21 when it was crowded with shoppers, firing from
the hip and hurling grenades at shoppers and staff.
The
gunmen coldly executed scores of people, with witnesses recounting how
in some cases they called out to those wounded, then finished them off
at close range.
The siege was declared over four days later.
Kenyan
police have named four of the attackers as Abu Baraal Al Sudani, Khatab
Ali Khane and one man known simply as Umayr -- reportedly all Somalis,
plus a Kenyan of Somali origin, Omar Nabhan. However, the names are noms
de guerre.