NAIROBI (AFP) - Kenyan troops have crossed the border into war-torn Somalia to attack Islamist Shebab rebels they accuse of being behind several recent kidnappings of foreigners, Kenyan officials said Sunday. "We have crossed into Somalia in pursuit of the Shehab, who are responsible for the kidnappings and attacks on our country," government spokesman Alfred Matua told AFP. An AFP reporter close to the border witnessed large numbers of troops, as well as military planes and helicopters overhead. Several witnesses reported heavy troop movement in Kenya's border regions, with truckloads of soldiers heading towards the frontier. The assault comes a day after Kenya's Internal Security Minister George Saitoti branded Somalia's Al-Qaeda-inspired Shebab rebels "the enemy" and vowed to attack them "wherever they will be". "Kenya is providing logistical and moral support," said Abdirahman Omar Osman, a spokesman for Somalia's Western-backed government, which controls the capital Mogadishu with the help of over 9,000 African Union troops. However, he said it was Somali forces in the south of the country that were "battling the Shebab on the ground". In just over a month, a British woman and a French woman have been abducted from beach resorts in two separate incidents, dealing a major blow to Kenya's tourism industry. On Thursday, two female Spanish aid workers were seized by gunmen from Kenya's crowded Dadaab refugee camp, the world's largest with some 450,000 mainly Somali refugees. Several tanks and military trucks crossed the border alongside "quite a number" of troops, a Kenyan internal security ministry official said, asking for anonymity as he was not authorised to speak to media. "There are those who entered Somalia today and many more troops will be following them afterwards," the official said. On Saturday, Somali government troops and allied militia wrested control of the Shebab-held town of Qoqani in the Lower Juba region, which borders Kenya, backed by heavy bombing by military aircraft. "Several aircraft dropped bombs on the jungle area of Qoqani causing heavy explosions, and the Shebab withdrew from the town without face-to-face fighting," said Sugule Ali, an elder in a nearby village. "The shelling was very heavy and we could hear the planes flying over the jungle as big bombs were dropped," Nuradin Haji Hassan, another witness, said.