Nairobi - Kenya's police chief on Tuesday admitted Tuesday that US President Barack Obama's weekend visit to Kenya was a security "nightmare", but said the incident-free trip to Nairobi had proved a major confidence booster for the country."My nightmare was that someone might sneak in and do something nasty," police Inspector General Joseph Boinnet said, referring to fears of attacks by al-Qaeda-affiliated Shabaab militants from across the border in Somalia. "But thank God what we had put in place worked and we are determined to keep them away from our borders, keep them away from our cities and keep this country safe," he added."We actually surprised ourselves," Boinnet said, asserting that Kenyan security officials were able to keep up with the demands of the US Secret Service. "Obviously they're much more advanced than us in terms of resources, but in our own little way we do our level best," he said."What we learnt is paying attention to the minutest detail."Subjugate the nativesHe also said working with the Americans had given Kenyan police - much maligned by the public due to endemic corruption and incompetence - a valuable lesson in conduct and how it needed to reform and overcome its poor image."The police force... was created by the British to subjugate the natives," he said. "We are no longer natives and we're no longer a force but a service. However, the reform process is still ongoing."Obama spent two days and two nights in Nairobi, the first-ever visit to the east African nation by a sitting US president. Kenya was the birthplace of Obama's father, making the trip especially emotional for both Obama and many Kenyans.Kenya's image as a regional hub has taken a battering in recent years due to political violence, rising crime and attacks by Somalia's Shabaab militants. The group were at the centre of security concerns during the visit, but there were no reported incidents in Kenya during Obama's stay.