Former US President Barack Obama on Tuesday used a tribute to Nelson Mandela to warn of "strange and uncertain times", a day after Donald Trump refused to challenge Vladimir Putin over interference in US elections. Delivering a speech in Johannesburg marking 100 years since Nelson Mandela's birth, Mr Obama made no direct reference to his successor but warned that the "politics of fear and resentment" were spreading across the world. Mr Obama criticised climate-change deniers, race-based migration policies, unbridled capitalism and "strongman politics" — all issues likely to be seen as veiled attacks on President Trump. #obamainkenya#obama#alertkenya