Police official informed, "After the Delhi incident, even Mumbai and Kolkata have been put on high alert. All policemen have been asked to remain alert and increase searches."
Two men on a motorbike fired several rounds on a tourist vehicle near Jama Masjid in Delhi, injuring two Taiwanese nationals.
A red alert has been sounded across the capital after the incident.
Mumbai has been on high alert following reports of presence of two alleged terrorists in the city during the Ganesh Chaturthi festival.