Indian police say they have arrested three people in connection with Thursday's bombings that killed 77 people in the northeastern state of Assam.

They say those arrested include a man whose cell phone was allegedly used by a little-known group called "Islamic Security Force - Indian Mujahedeen" to send a text message claiming responsibility for the blasts.

Senior police official Bhaskar Jyoti Mahanta says two other people were taken into custody because their car and motorcycle were believed used in the bombings.

Also Saturday, Indian Prime Minister Manmohan Singh traveled to Guwahati, the capital of Assam state, to visit some of the 300 people wounded in the blasts.  At least 12 bombs exploded within an hour of each other in four towns.

Authorities have been trying to identify the authenticity of the text message sent by "Islamic Security Force - Indian Mujahedeen."  The group came into existence in 2000 mainly to thwart attacks by indigenous tribespeople on Muslim settlers in Assam state.

The group's name is similar to one that claimed responsibility for three deadly bombings earlier this year in Jaipur, Gujarat and New Delhi.

Assam's main separatist group, the United Liberation Front of Asom, or ULFA, denied any involvement in Thursday's bombings.  Police have said the size and complexity of the attack may indicate the work of a fairly sophisticated group.

Separatist violence in northeastern India has killed some 20,000 people since 1979.  The region also has been plagued by ethnic conflict and attacks that authorities blame on Muslim extremists based in Bangladesh.

Some information for this report was provided by AFP, AP and Reuters.