Pope Francis was obviously in a hurry to start his trip to Africa: The pope's flight touched down a few minutes ahead of schedule at Nairobi's international airport. A relaxed-looking pope smiled and waved at traditional dancers, dressed in bright colors, who greeted him singing "Karibu (Welcome to) Kenya Papa." President Uhuru Kenyatta, a Catholic, was leading political and religious dignitaries who welcomed the pontiff at the airport.

Large crowds of people lined the road from the airport to the city and waved as the pope's motorcade whisked by. Sticking to his line of preaching a simple and humble lifestyle, the pope rode in a gray Honda, instead of an official limousine.

A clear message to Kenya's elite

The pope used his address at State House, the seat of Kenya's president, for a clear message to Kenya's political elite. "I encourage you to work with integrity and transparency for the common good," he said. The pope also urged Kenya's leaders "to show genuine concern for the poor."

It's a message many Kenyans have been waiting for. Their country is among the most corrupt nations in the world. On Transparency International's corruption index, Kenya is ranked 145 out of 175 countries. President Kenyatta's government has come under fire after a number of corruption scandals.

"The visit offers an opportunity for the country and its leadership to re-orient our national values towards the pursuit of noble goals for the benefit of humanity," Kenya's top-selling newspaper "Daily Nation" had said in an editorial on the day of the pope's arrival.

'A culture of conservation which gives you honor'

The pontiff also emphasized two other key themes on his African trip: Poverty and environment. "Experience shows that violence, conflict and terrorism feed on fear, mistrust and the despair born of poverty and frustration," the pope said.

He called on the international community to step up its effort to protect the environment, warning of a grave environmental crisis facing the world. At the same time, he praised the traditional respect for nature in many African societies. "Kenya has a culture of conservation which gives you honor," he said.

Kenyan president pledges to root out corruption

Kenya's President Uhuru Kenyatta appeared humble, almost submissive in his welcoming speech. "We are honored, humbled and privileged that you have chosen to start your Apostolic voyage to Africa here in Kenya," he told the pontiff.

Kenyatta asked the pope for his prayers in the fight against corruption. "In the heart of every Kenyan we know we need to win it and it falls on me to lead it," he said. He also emphasized that the pope's visit was a chance for Kenya to end religious and ethnic divisions.

President Kenyatta has come under fire over his reluctance to act on a number of corruption scandals in his government. For weeks, the president resisted calls from civil society and opposition Members of Parliament to sack Devolution Minister Ann Waiguru after millions of euros went missing in her ministry.

Just hours before the pope arrived, the president reshuffled his cabinet and announced new anti-corruption legislation. Many Kenyans have dismissed the moves as window-dressing.

Tight security

Security has been tightened in Nairobi ahead of a public mass on Thursday. More than 10,000 police officers and 10,000 members of the National Youth Service will be deployed. For security reasons, major roads leading in and out of the city center will remain closed. More than 1.4 million people are expected to attend the mass on the city's university campus.

On the flight to Kenya, the 78-year-old pontiff had dismissed security fears about his trip to Kenya and Uganda. Both countries have been the target of terrorist attacks of the Islamist Al-Shabaab militia in recent years. “To tell you the truth, the only thing I'm worried about is mosquitos," he told reporters.

Pope Francis is running on a tight schedule in Kenya, which will also see him meeting leaders of other religions present in Kenya, as well bishops and other clergy, and visiting a slum. The pope will also address Kenya's youth at a special ceremony on Friday.