Article published on the 2008-10-31 Latest update 2008-10-31 15:27 TU
"The Islamic Security Force-Indian Mujahedeen takes the responsibility for yesterday's blasts," said the text message to the Newslive television network.
It want on to say that further attacks are likely.
"We warn all of Assam and India for situations like this in the future and we thank all our holy members and partners," it said.
"We understand that the person from whose cellphone this text message was sent has been arrested," local reporter Zarir Hussein told RFI. "And now police are investigating his possible links with this so-called Islamic Security Force-Indian Mujahedeen group."
Police say that the group seems to have come into existence in 2000 in the west of the state, where tribal Bodo militants are campagining against Muslim settlers from nearby Bangladesh.
The separatist United Liberation Front of Asom was previously under suspicion and a dozen people were questioned about the attacks on Friday.
There were clashes between police and about 200 protesters who blamed the blasts on lax security on Friday. That followed the lifting of a curfew imposed Thursday when residents attacked fire engines which were trying to fight a series of fires.
Prime Minister Manmohan SIngh has announced that he will visit Assam Saturday. He called the attacks "barbaric acts targeting innocent men, women and children".