"Increase in communal incidents in the country in the past few months and the revival of ethnic tensions in the North East in recent weeks have been particular causes of concern to all of us," he said, addressing the annual DGPs/IGPs conference here.
Singh said ethnic disturbances of the North East assumed a national dimension with the flight of people belonging to the region from various towns of South and Western India.
"This further strained the communal situation in the country, which was already showing some signs of deterioration, particularly in the states of Uttar Pradesh, Madhya Pradesh, Maharashtra, Karnataka and Kerala," he said.
The Prime Minister said use of bulk SMSes and social media to aggravate the communal situation was a new challenge that the recent disturbances have thrown before the country.
"We need to fully understand how these new media are used by miscreants. We also need to devise strategies to counter the propaganda that is carried out by these new means," he said.
Singh, however, cautioned that any measure to control the use of such media must be carefully weighed against the need for the freedom to express and communicate.
"I am sure that, in the coming months, our police forces would be able to work out effective strategies to deal with these tendencies," he said.
The Prime Minister said ethnic, religious and cultural diversity in our country is a source of strength and vitality to India and efforts must be taken to strengthen the thread of unity running through country's "variegated societal landscape".