An explosion killed a Kenyan policeman and wounded four civilians Wednesday in the northeast of the country near the border with Somalia, a police commander said. It was unclear what caused the explosion at a border area in Mandera, one of Kenya\'s drought-ravaged regions. \"We have lost a police officer after an explosive along the border in Mandera, four other people have been taken to hospital with injuries,\" the region\'s police chief Joseph Ole Serian said. Somalia\'s Al Qaeda-affiliated Shebab rebels have made several cross border raids in the past. The group has repeatedly threatened to attack Kenya for supporting the Western-backed Somali government.