Three almost simultaneous blasts rocked three different locations in India's financial capital of Mumbai during evening rush hour on Wednesday, killing at least 17 people, police said.
Police did not want to speculate on the nature of the blasts, two of which were in south Mumbai, while the third was in the centre of the coastal city. All three locations are crowded parts of the city, especially during rush hour.
India has remained jittery about the threat of militant strikes, especially since the Mumbai attacks in November 2008 which killed 166 people and raised tensions with arch rival Pakistan.
Television footage from CNN-IBN television channel showed some debris at one suspected blast site.
Authorities said at least 75 people were wounded.
A Home Ministry spokesman said it was too early to comment on the nature of the blasts.
"We were inside our office when we heard a huge noise. Outside there was a lot of commotion, we can see fire trucks are here and they have taken away two or three bodies," Jasraj Jain, a witness, told CNN-IBN television.
The popular Opera House area and Zaveri Bazaar in south Mumbai were where two of the blast occurred. The third blast was in Dadar, which is in the centre of the city.
New Delhi says Pakistan-based groups aid and train militants to carry out attacks against India, a claim Islamabad rejects.
Home-grown militant groups are also active in the country and have in the past few years carried out attacks in large cities.