Anticipating a strike by Pakistan-based terror outfits in the country, particularly the metros, in the aftermath of Army's surgical strikes in PoK, the home ministry has issued an alert seeking stepped up vigil at strategic installations, industrial complexes, crowded places, airports, historical monuments and government buildings across the country. The alert identified Delhi, along with Rajasthan, Punjab, Jammu & Kashmir, Maharashtra and Gujarat as possible targets. Intelligence sources, citing credible inputs, said there was a strong possibility of Pakistan's ISI directing a highly motivated and heavily armed terror cell to carry out a strike in the capital.

The threat posed by these groups has decreased since some of their cells were neutralized while others switched their allegiance to Islamic State. But local sleeper cells which take their cue from ISI have not been totally eliminated and could be activated, the agencies fear.

The fact that October is packed with festivals was highlighted in the advisory which sought tighter police bandobast at crowded places and puja pandals. Apart from this, CISF has been tasked with tightening security at airports and monuments such as Taj Mahal and Red Fort. Tighter access control has been sought at all buildings housing key government offices, particularly in the national capital.

An intelligence officer said the state of high alert across the country may continue through October.

"A retaliation by Pakistan to the surgical strikes is foreseen over the next 10-15 days. However, given that Diwali falls on October 30, the alert will last till then," he said.