(CNN) -- All metropolitan areas in India were on high alert Sunday after 17 blasts hit the western city of Ahmedabad within a little more than an hour, killing at least 29 people, according to police and government officials.
Flames rise from vehicles after an explosion in Ahmedabad, India, on Saturday.
Another 88 were wounded in the Saturday night attacks, they added.
"I appeal to the people of Gujarat to remain calm and not let these terrorists be successful in instilling fear," said Narendera Modi, chief minister of Gujarat state, which encompasses Ahmedabad.
Several media outlets and the country's Intelligence Bureau received an e-mail, purportedly from the Muslim militant group Indian Mujahedeen, warning about a possible attack. The group has claimed responsibility for two similar attacks in the past nine months in northern India. Watch how the media was tipped »
But afterward, the Islamic militant group Harkat-ul-Jihad al-Islami, the Movement of the Islamic Holy War -- known as HuJi -- claimed responsibility for the bombings, said CNN-IBN, CNN's sister network.
Cross-pollination between terror groups can make it difficult to separate them, analysts said.
All of the explosions were of low intensity, and most went off in eastern Ahmedabad, within a 10-kilometer (6.2-mile) radius, according to CNN-IBN.
One explosion was at a bus stop, others at a railway station and on a bus. Several went off at or near hospitals where the injured were being taken. Watch the commotion at one blast scene »
Video footage from the scene of one explosion showed charred and twisted bicycles and motorcycles lying on the street as a crowd milled around. At least one of the bombs was on a bicycle, authorities said. Others were in tiffin boxes, a type of lunchbox used by Indian adults.
The blasts began about 6:30 p.m. and lasted until about 7:40 p.m., according to CNN-IBN.
Leaders including Prime Minister Manmohan Singh condemned the explosions.
Indian Mujahedeen claimed responsibility in May for near-simultaneous bomb attacks that killed 63 people in the northwest Indian city of Jaipur. In that claim, the group declared "open war" against India in retaliation for what it said were 60 years of Muslim persecution and the country's support of U.S. policies.
The group also claimed responsibility for near-simultaneous blasts outside courts in three northern Indian cities in the state of Uttar Pradesh in November. More than a dozen people were killed and 80 injured.
In both the Jaipur and the Uttar Pradesh bombings, one of the blasts came from an explosives-laden bicycle.
In May, security analysts described Indian Mujahedeen as a relatively unknown group. It may be a new home-grown terror network, an alias for an existing group or a foreign militant organization.
The blasts come a day after nine small explosions went off in the city of Bangalore, CNN-IBN reported. Two people were killed and six injured.
"The blasts seem to be along the lines of yesterday's Bangalore blasts," Union Minister of State for Home Sri Prakash Jaiswal said. "It is a conspiracy to unsettle the country."
Officials said they believe that the goal of the explosions was to create panic, not to kill a large number of people.
CNN's Bharati Naik, S. Gopal and Sara Sidner contributed to this report.