The Prime Minister Dr Manmohan Singh today cautioned people against the threat of extremism and communalism, saying they are two of the greatest challenges facing the nation. Addressing a function in New Delhi to present national communal harmony awards 2009 and 2010 , Dr Singh said that the people have to work collectively in strengthening communal amity and brotherhood in the country.Dr Singh said, there are elements who want to create discord in the society and this has to be fought resolutely. Recalling the rich traditions of communal harmony and brotherhood, Dr Singh complimented the awardees for their outstanding contribution in fostering bond of communal amity.Addressing the function, Vice President Md Hamid Ansari said that the promotion of communal harmony by the State is the fundamental necessity to preserve social integrity. He said that the government has no choice but to intervene in times of communal disharmony. He called for a pervasive and preventive approach and conscious programme to promote communal harmony in the country.The Vice President conferred the awards on Dr Mohommad Hanif Khan Shastri and Acharaya Lokesh Muni in the individual category while the Centre for Human Rights and Social Welfare, Rajasthan in the Organisation category for their outstanding contribution in the field.Home minister Mr P Chidambaram said on the occasion that these institutions and awardees have contributed significantly in strengthening national integration.