According to reports an email notice about the attack went out minutes before a series of blasts rocked Delhi.

The email, claiming responsibility for the bomb blasts in India's capital Delhi on Saturday, was sent five minutes prior to the actual explosions, media organisations said.

The email, sent by a poster claiming to be from the Indian Mujahideen, said that Delhi was about to be hit with blasts, and the militant organisation would strike other locations in India. The email, which was sent to news organisations in India including Zee News, was sent from a Yahoo email account that was traced back to a Mumbai address.

On further investigation, it was determined the email was sent around the time of the first blast, Parambir Singh, additional commissioner of Mumbai police's antiterror unit told the Press Trust of India on Sunday.

A coordinated stream of five bombs exploded in different areas in Delhi on Saturday evening, including densely populated areas, killing close to 30 people. More bombs were being defused, according to media reports.

India has recently witnessed a spate of serial bomb blasts that has put the country and IT industry in a state of alert. Recent explosions in the cities of Ahmedabad and IT capital Bangalore in July claimed the lives of 56 people.

Several suspects are being held while others being pursued, but initial details point to a trend in the way responsibility is claimed for serial blasts. The Indian Mujahideen claimed responsibility for the earlier Ahmedabad blasts five minutes prior to the 21 serial bomb blasts that rocked the city. The email address was ultimately tracked down to a hacked Wi-Fi account of Kenneth Haywood, a US executive working for a firm in Mumbai. Feeling the heat of being at the cnetre of an intense investigation by India's authorities, Haywood fled for the US and returned recently after his name was cleared.

A number of international companies have offices in or around Delhi, including top Indian IT companies Tata Consultancy Services, Infosys and Wipro. No company immediately responded to comment on any potential impact of the blasts on operations.

Security has been tightened up in Mumbai, where a Hindu festival resulted in crowds on the streets on Sunday. Security officials screened passengers through train stations with metal detectors and a number of roads were blocked for vehicle inspection.