India, May 9 -- As Pakistan intensified attempts to hit various installations along India's western borders, the tricity observed a three-hour blackout on Thursday night as a pre-emptive measure.

Air raid sirens went off around 9.30 pm with the administrations of Chandigarh, Mohali and Panchkula snapping power till midnight.

In view of the rapidly changing situation, the administrations of the three cities have declared a holiday in all government and private schools on Friday and Saturday.

Panjab University also has postponed all exams scheduled for May 9, 10 & 12.

Additionally, security was beefed up around all key installations in the tricity, including the Shaheed Bhagat Singh International Airport, Doordarshan Kendra, Sector 37; ...