The leader of the Somali group affiliated with al-Qaeda said the attacks will continue until Kenyan troops are withdrawn from Somalia.
The leader of al-Shabab said in a message that there is no way Kenya can "withstand a war of attrition inside your own country."
"Make your choice today and withdraw all your forces," said Ahmed Abdi Mohamed Godane, who goes by his nom de guerre Mukhtar Abu Zubayr, in a new statement posted on the Internet late yesterday.
Al-Shabab said the Nairobi mall attack was not only directed at Kenya, but was also "a retribution against the Western states that supported the Kenyan invasion and are spilling the blood of innocent Muslims in order to pave the way for their mineral companies," according to the statement from Godane.
Al-Shabab attacked Nairobi's upscale Westgate mall Saturday and held it for four days in a siege in which at least 67 people, including three Indians, were killed.
Forensic experts from around the world, including the US, Britain, Germany and Canada, continued their work today reconstructing events in the crime scene including by carrying out fingerprint, DNA and ballistic analysis.
Last night, al-Shabab attacked the border town of Wajir, 390 kilometres southwest of Mandera.
One person was killed and four wounded after a gunman opened fire and threw grenades.
Kenya has suffered many such attacks by al-Shabab along its 682 kilometre border with Somalia but they take on new significance following the Westgate Mall attack.
