“Terror attack in Pakistan near Wagah Border is shocking. I strongly condemn such a dastardly act of terrorism,” Modi said on his Twitter account.
“My condolences to the families of the deceased. Prayers with the injured.”
India has stepped up security along its side of the border in the wake of the attack near the Pakistani city of Lahore that tore through crowds of spectators leaving after a daily ceremony to close the frontier.
The explosion, which wounded more than 120, came at Wagah border gate after the “flag-lowering” ceremony, a display of military pageantry that attracts thousands of spectators every day on both sides of the border, and is popular with foreign tourists.
R.P.S Jaswal, deputy inspector general of India’s Border Security Force which guards Wagah, said security has been increased although “our side is secure”.
“A red alert has been issued keeping in view the blast across the border in … Pakistan,” Jaswal told AFP by phone from his base near the Indian city of Amritsar.
The neighbours have had frosty relations since independence from Britain in 1947, fighting three full wars, two over the Himalayan territory of Kashmir.
Sunday’s attack comes amid heightened tensions between the nuclear-armed countries after a resurgence of cross-border shelling along the disputed frontier in Kashmir.