New Delhi  - As many as 40 people were injured, 18 of them seriously, in a bomb blast carried out by separatist militants in India's north-eastern state of Assam on Thursday, news reports said.

The bomb, which was planted on a bicycle, blew up in a busy market in Howraghat town, some 250 kilometres east of Assam's main city Guwahati, the PTI news agency said.

According the PTI report, militants belonging to the Karbi Longri National Liberation Front (KLNLF) detonated the explosive. The 18 seriously wounded persons were moved to a state-run hospital in neighbouring Nagaon district.

State police however contradicted the PTI figures, saying only 29 were injured and none of them sustained serious injuries, said Howraghat police station chief, Anil Choudhury.

"We suspect KLNLF is behind the trouble as intelligence inputs indicated that the KLNLF has planned to carry out a number of blasts in the district," Choudhury said.

The KLNLF has been leading an armed struggle for a homeland for Karbi tribals living in two hill districts of Assam, Karbi Anglong and North Cacher.

Several militant outfits with demands ranging from autonomy to secession are active in the north-eastern state. More than 20,000 people have been killed in violence in the state since 1979.(dpa)