A mass shooting in a shopping mall in the Kenyan capital on Saturday might be a "terrorist" attack, Kenya's Ministry of Interior said.

"It is a possibility that it is an attack by terrorists, so we are treating the matter very seriously," Mutea Iringo, the principal secretary in the Ministry of Interior told Reuters.

Asked if foreign security services were involved in the operation to flush out the attackers, he said, "At this stage it has not become necessary yet."