"The period before and after the Republic Day is an especially vulnerable period. The government has sensitised states and asked them to remain at the highest level of alertness," Home Secretary Madhukar Gupta told reporters.
"States have upgraded their Intelligence gathering machinery and undertaken a number of measures to prevent and counter terrorist threats," he added.
"Nevertheless, there are a number of terrorist, extremist and insurgent groups which continue to pose a serious threat to the security of the country," he said.
Gupta has held discussions with the Delhi Police to ensure that Republic Day passes off peacefully and added, "the Home Minister has held meetings to review the security scenario."
OneIndia News (With inputs from Agencies)