Around 21 people were killed in a three bomb blasts that have rocked the most crowded areas of Mumbai on Wednesday.  

Officials visited the blast sites on Wednesday where 21 people were killed and more than 141 were injured.

About five hours after the explosion Union Home Minister P Chidambaram visited the scene to get an assessment of the scene of the triple blasts.

The three separate bombs went off in crowded districts of Mumbai during the evening rush hour.

Since 2008, these blasts were the biggest militant attack on India's financial capital.

No organization has claimed the responsibility for the blasts.

The two of the bombs were planted in a motorcycle, and the third was concealed under an umbrella placed by the roadside, the official said.

The low-intensity explosions went off at Zaveri Bazaar, Opera House and Kabutar Khana in Dadar, which are all densely-crowded places during the evening rush hour, Mumbai police said.

Around 12 people were killed at Zaveri Bazaar, and nine at Opera House. No deaths were reported in Dadar though there were eight people who were injured.

Chidambaram said the blasts a coordinated attack by terrorists, while Chief Minister Prithviraj Chavan said it was another attack on the heart of India, media reported.