Prime Minister Atal Behari Vajpayee has called for calm, saying the violence is wrong and "a disgrace to the nation".
In the town of Surat, reports say a gang set petrol stations on fire and attacked a TV station, killing at least four workers there.
Those living in Ahmedabad are now too scared to leave their homes.
About 80 Muslim living in one apartment block said they haven't had anything to eat for three days.
The rioting started on Wednesday after Muslims attacked a train in the town of Godhra that was carrying Hindu protesters. Nearly 60 of them were killed.