Assam's fragile peace was shattered Monday when tribal separatists killed at least 18 Hindi-speaking people, including eight bus passengers, in three separate attacks in the northeastern state of Assam, officials said.

Eight people were also injured in the attacks.

A police spokesperson said heavily armed militants of the outlawed National Democratic Front of Bodoland (NDFB) fired at a bus near Bhoimari village in Sonitpur district, about 250 km north of Assam's main city of Guwahati. They lined up the passengers and took away the Hindi-speaking people to the forest and shot them.