Kenyan policeman killed by Somali rebels

ISIOLO, Kenya, July 27 (Reuters) - A Kenyan policeman was killed near the Somali border on Wednesday in a bomb attack by the same rebels who are being blamed for blocking food aid to Somalia's famine victims, government officials said.Three other policemen were injured in the attack when a remote-controlled device was detonated beside a tree where they stop for a break at the same time every day."We have lost one of our officers in Mandera this morning at around 11.30am and three have sustained injuries," Philip Ndolo, commissioner of Kenya's northeastern province police, told Reuters.Ndolo said the bomb was triggered by mobile phone from the Somalia side of the border.A heavy contingent of Kenyan security forces have been deployed at the border and analysts say they may be planning a joint offensive with the Somali government against al Shabaab rebels hiding in the area, which is now government-controlled.The drought gripping the region straddling Somalia, Kenya and Ethiopia is the worst for 60 years, some aid groups say, and is affecting more than 12 million people. In the worst-hit areas in Somalia, famine has been declared and 3.7 million people are at risk of starvation in the country.Much of southern and central Somalia is controlled by the al Shabaab Islamist militants linked to al Qaeda who imposed a ban on food aid in 2010. They have since lifted the ban but maintained the embargoes on the U.N food agency and several other aid agencies.About 1,500 refugees a day are streaming over the Somalia border and into Kenyan refugee camps in search of food