Some of the bombs in the second wave targeted the hospitals where the injured were being taken, he adds.
"We saw a blue bag near the trauma centre, and before we could react we saw it explode in a shine of blinding light, and some 40 people were hit by flying shrapnel," doctor Vipul Patil, at the Dhanwantari Hospital, told AFP news agency.
Ahmedabad is an ethnically diverse city which has suffered from political instability in the past.
Riots broke out there in 2002 between Hindus and Muslims.
Reports suggested many of Saturday's blasts were in the city's crowded old quarter - a religiously-mixed area.
Analysts believe the attack may be linked to the Bangalore bombs and could be designed to whip up trouble between religious communities.
Prime Minister Manmohan Singh has appealed for people to remain calm.
India has been hit by several waves of bombings in recent years. Targets have ranged from mosques and Hindu temples to trains and courthouses.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.