The United Liberation Front of Asom is said to have claimed responsibility for blasts in four places in Assam since Saturday.
A caller, identifying himself as ULFA commander-in-chief Paresh Barua, told a local daily over telephone on Sunday night that the blasts were in response to Assam Chief Minister Tarun Gogoi's call for a ceasefire.
The ULFA had already rejected the CM's conditional ceasefire offer but had said it would consider a proposal of talks with the Centre only if it came out with a "written commitment to discuss the sovereignty issue".
Barua had earlier said that the CM was just the head of a "puppet government put into place by the Centre, and he has no authority to present an offer of ceasefire".
The state government on September 30 offered a conditional ceasefire provided the banned outfit stops all violence. It asked the ULFA to respond within a fortnight so that ceasefire could be declared from October 16.