By PP Singh BBC correspondent in Guwahati

They said militants carried out at least three attacks on villagers belonging to the rival Karbi tribals on Tuesday night.

Officials said the attacks took place in the hilly Karbi Anglong district when the villagers were asleep.

The biggest attack was reported from Sorpo Teron village where 18 people were killed.

Suspected militants struck at two others villages - Oden Tisso where they killed four and Jari Teron village where five people were killed.

Assam's chief minister Tarun Gogoi has ordered police reinforcements to the affected area.

History of violence

Mr Gogoi has also asked his home minister to immediately visit the three villages and report on the steps being taken to check the violence.

Karbi Anglong district has been the scene of ethnic violence between tribals and non-tribals over the past few years.