After joyous celebrations in Nairobi where some greeted Francis in traditional feather headdresses, bright clothes, and beads, the 78-year-old pontiff went to Kenya's presidential palace to deliver a more sombre message. "Experience shows that violence, conflict and terrorism feed on fear, mistrust, and the despair born of poverty and frustration," he said alongside President Uhuru Kenyatta. "I encourage you to work with integrity and transparency for the common good, and to foster a spirit of solidarity," he said in comments alluding to the corruption and inequality that blights the country. Kenyatta called corruption a scourge and said his administration was committed to fighting it. "We sacrifice our people and our environment in the pursuit of illegal profit," he said. Days before a key UN climate change summit in Paris, COP21, the leader of the world's 1.2 billion Catholics warned the world was facing a "grave environmental crisis". "There is a clear link between the protection of nature and the building of a just and equitable social order," said Francis who has taken on a vocal role in environmental issues. His message is likely to resonate in Africa where climate change is already felt and where wildlife poaching is rampant. The pontiff will also visit Uganda and troubled Central African Republic (CAR) before flying back to Rome on Monday. On a trip fraught with security concerns, thousands of police and troops have been deployed, with key roads closed in the capital Nairobi to ensure the visit is peaceful.