Nairobi - US President Barack Obama arrives in his ancestral homeland Kenya late on Friday, with a massive security operation under way to protect him from al-Qaeda-linked Somali militants.Obama, making his first visit as president to his father's birthplace, will address an entrepreneurship summit and hold talks on trade and investment, security and counter-terrorism, and democracy and human rights.Parts of the Kenyan capital Nairobi have been locked down and airspace will be closed during the president's arrival late on Friday and his departure late Sunday, when he travels up the Rift Valley to neighbouring Ethiopia, the seat of the African Union.At least 10 000 police officers, roughly a quarter of the entire national force, have been deployed to the capital.Top of the list of security concerns is Somalia's Shabaab militants, who have staged a string of suicide attacks, massacres and bombings on Kenyan soil, including the bloody attack on the Westgate shopping mall in the heart of the capital nearly two years ago that left 67 dead."Welcome Obama"Excitement has been building in Kenya for weeks, with the visit painted as a major boost for the country's position as an African hub - something that has taken a battering in recent years due to Shabaab attacks and political violence that landed Kenyan leaders in the International Criminal Court."I need not tell you how eagerly we have all waited for the day, or how keen we all are to make it the most memorable of homecomings," Kenyan President Uhuru Kenyatta told reporters."It's a vote of confidence for our city and our country," Nairobi Governor Evans Kidero also told AFP.He has overseen a clean-up campaign in Nairobi, including the filling of potholes, sweeping of streets, the repainting of faded road markings and laying new pavements on once muddy sidewalks.The two main newspapers carried the same simple headline "Karibu Obama" - "Welcome Obama" in Swahili. The Standard newspaper promised a "spectacular reception for a son of the soil".Kenyatta, writing in the Daily Nation, said that "many are the ties, not just of friendship, but also of family" between Obama and Kenya.Crimes against humanityObama is celebrated as a hero throughout the country, yet many Kenyans have been disappointed it has taken him until almost the end of his second term in office to make the trip.A presidential visit to Kenya had been put on ice while Kenyatta faced charges of crimes against humanity for his role in 2007-2008 post-election violence. The ICC has since dropped the case, citing a lack of evidence and accusing Kenya of bribing or intimidating witnesses.Kenyatta, however, has signalled that his controversial Deputy President William Ruto, still on trial at the ICC and outspokenly homophobic - having describing gays as "dirty" - would be present when government officials meet Obama.Asked whether gay rights would be discussed, Kenyatta said it was "a non-issue".But Obama, in an interview with the BBC, said he was "not a fan of discrimination and bullying of anybody on the basis of race, on the basis of religion, on the basis of sexual orientation or gender", and that this would be "part and parcel of the agenda".Counter-terrorism will also be a key topic for discussion, with Nairobi the scene of one of al-Qaeda's twin 1998 US embassy bombings.Heavy security restrictions"The fight against terror will be central, we have been working in very close co-operation with American agencies," Kenyatta said. "Poverty, improved health for our people, better education, better roads, better security, these are our key focuses."Obama is due to address an international business summit in Nairobi on Saturday, an event the US embassy itself warned could be "a target for terrorists"."The American president is a high-value target so an attack, or even an attempt, would raise the profile of Shabaab," warned Richard Tutah, a Nairobi-based security and terrorism expert.Mitigating that is an overwhelming security presence in the capital, which regional security analyst Abdullahi Halakhe described as "suffocating".Hundreds of American security personnel have arrived in Kenya in recent weeks.Obama himself bemoaned the heavy security restrictions earlier this month."I will be honest with you, visiting Kenya as a private citizen is probably more meaningful to me than visiting as president, because I can actually get outside of the hotel room or a conference centre," Obama said.