The 23-year-old Norwegian citizen has been identified as Hassan Abdi Dhuhulow.
"The man being investigated by Norwegian police over the attack on Kenya's Westgate shopping centre is Hassan Abdi Dhuhulow," BBC reported.
"The 23-year-old Norwegian citizen of Somali origin is suspected of helping to plan and carry out the attack," it said.
A relative of Hassan told BBC that he left the town of Larvik for Somalia in 2009.
The total number of militants involved in the attack is still unclear.
More than 60 people were killed in the attack in the shopping mall.
Somalia-based militant group Al Shabab, that opposes Kenya's participation in a peacekeeping mission in neighbouring Somalia, has claimed responsibility for the attack.
--IBNS (Posted on 18-10-2013)