New Delhi, Feb 7 : The Prime Minister, Dr Manmohan Singh, on Sunday described terrorism as the biggest threat to the country, and added that internal and border security would be tightened to counter it.

"We must fight united, an attempt is being made so that all investigating agencies for together for a common purpose," Dr Singh said.

Addressing an internal security meeting of all State Chief Ministers convened by him to discuss internal security and issues related to terrorism, Dr Singh said Naxalites have emerged as a major threat to the country and have refuted all efforts for talks with the Centre.

He further said that insurgents and terror groups were also a threat to national security.

"Jammu and Kashmir, north-east bear the brunt of the terror groups," he said, adding that hostile groups acting from across the border are working to perpetrate their activities on Indian soil.

Dr Singh said the security situation affects growth; inadequate cops as well as less number of trained cops were also a reason for worry.

"We need to fill vacant police posts and states should act quick on this," Dr Singh said, adding that the country needs a safer coastline.

"We must periodically review the security system," he said.

Earlier, Union Home Minister P Chidambaram said the Centre would boldly confront all challenges thrown at it by Naxalites.

Today''s meeting was called by Dr Singh to discuss internal security and issues related to terrorism. (ANI)