President Hu Jintao yesterday urged a military force in charge of internal security to step up its training to deal with social unrest, unexpected events and terrorism. In a rallying call to the People's Armed Police, Mr Hu praised officers for their 'outstanding contribution' in major tasks last year, which included putting down the riots in Tibet in March and providing security for the Beijing Olympics. But he warned the challenges this year would be 'hard and complicated', Xinhua reported. The nation will mark several sensitive anniversaries this year, including the 50th anniversary of the Tibet uprising, 20th anniversary of the Tiananmen protests and 60th anniversary of the People's Republic. The country is also facing rising social tensions as the economy slows down. Millions of jobless migrant workers are returning to the countryside, sparking fears of unrest.