Security in the national capital and at other vital installations throughout the country was tightened even as extra-precautionary measures were in place for the Delhi-Lahore bus service following strike by militants on the Delhi-Attari special express that left 66 dead.

Road barricades were immediately placed by the Delhi Police at various intersections and security was tightened at the railway stations in the national capital after the blasts besides increasing the security measures at the Ambedkar bus terminus from where 'Sada-e-Sarhad,' which is scheduled to leave for Lahore on Tuesday.

Access control at all the government offices was being monitored closely while strict vigil was being kept at all entry and exit points of the national capital.

Specific instructions have been issued to security agencies to keep a special watch at places of religious congregations, which could be sensitive targets of militant groups, sources said.

In the national capital, which witnessed serial blasts in 2005, Delhi Police have sensitised shopkeepers in busy market areas to remain vigilant on any suspicious-looking person or activity. Metal detectors have been placed at all the entrance points of the busy markets and frisking of the people.

In airports throughout the country, the already alert security was further beefed up with additional rounds being conducted by the Quick Reaction Team.

The nuclear facilities throughout the country, which have been on top of the militant lists, were also asked to further tighten the security.