Kenyan bus attack kills 28; Islamists claim responsibility NAIROBI (Reuters) - Somalia's al Shabaab Islamists said they staged an attack in Kenya on Saturday in which gunmen ordered non-Muslims off a bus and shot 28 dead, while sparing Muslim passengers. Three of the group led out to be killed saved their lives by reciting verses of the Koran for the militants, a local security official said. Al Shabaab said its men had ambushed the Nairobi-bound bus outside Mandera town, near Kenya's border with Somalia and Ethiopia, and killed the non-Muslims in retaliation for raids on mosques in the port city of Mombasa. Early this week, police in Mombasa shot dead a man and arrested over 376 others when they searched four mosques in the port city that they said were being used to recruit militants and stash weapons. "The Mujahideen successfully carried out an operation near Mandera early this morning, which resulted in the perishing of 28 crusaders, as a revenge for the crimes committed by the Kenyan crusaders against our Muslim brethren in Mombasa," Sheikh Ali Mohamud Rage, al Shabaab's spokesman, said in a statement. Islamist militants use the term "crusaders" to describe Christians or non-Muslims in general. Police Inspector General David Kimaiyo told reporters that 19 men and nine women were killed. "Preliminary reports indicate that the attackers, who were heavily armed, later fled toward the border into Somali," he said. A witness to the ambush, who asked not to be identified, said the attackers boarded the bus and tried to identify Muslims and non-Muslims. Ahmed Maalim, an official at the Mandera East sub-county security force, said the attackers ordered passengers thought to be non-Muslims out of the bus. Three were spared after reciting Koranic verses and ordered back on the bus. The women and men (remaining outside) were separated, then shot at close range. None survived," he said. In response to the attack, Kenya Defence Forces (KDF) launched ground and air raid and destroyed a camp believed to have been used by the attackers. "The KDF operation will continue until they arrest the attackers," said Col. David Obonyo, KDF spokesman. Al Shabaab claimed responsibility for a 2013 attack on Nairobi's Westgate shopping mall that killed at least 67 people and attacks in Lamu in June and July that killed at least 65. The group has vowed to drive Kenyan and other African Union peacekeeping troops out of Somalia. Saturday's attack showed al Shabaab remains able to strike both in Somalia and abroad despite the killing of its leader Ahmed Abdi Godane in September. The Mandera region is awash with guns due to its proximity to Somalia, where al Shabaab has been fighting to topple the government, and Ethiopia, whose armed Oromo Liberation Front has made incursions into Kenya. Insecurity plagues East Africa's biggest economy, prompting Western nations to issue travel warnings and hitting the tourism industry, a major source of hard currency. Additional reporting by Feisal Omar and Abdi Sheikh in Mogadishu, Humphrey Malalo in Nairobi and Noor Ali in Isiolo; Editing by Andrew Roche