The national capital is on high alert following intelligence inputs indicating a possible terror threat. This prompted the Delhi Police and other security agencies to intensify vigil across several sensitive locations, sources said on Saturday. A source said security has been increased at the Bharatiya Janata Party (BJP) headquarters on Deen Dayal Upadhyaya (DDU) Marg and nearby government establishments, with additional deployment of armed personnel, barricading and intensified vehicle checks.