"Attacks in London are shocking and anguishing. We condemn them. My thoughts are with families of the deceased and prayers with the injured," Modi tweeted soon after his return from a four-nation Europe tour where the fight against terrorism formed a major part of his agenda.
At least six people were killed and 30 others injured in two separate terror attacks in London.
According to Met Police Assistant Commissioner Mark Rowley, a van struck people on the London Bridge. It then across the bridge knocking over several pedestrians.
The van was heading towards the London Bridge station, on the south bank of the river.
The vehicle then continued to drive towards Borough Market, just south of the bridge, where three assailants got out and attempted to stab civilians in a restaurant, including a police officer.
Armed police were called to the scene and within eight minutes, the three assailants were shot dead.
This is the third terror attack in Britain since March.