N`djamena: At least 19 Boko Haram fighters and two Chadian soldiers were killed in combat on Friday after the insurgents attacked a Chadian village on the banks of Lake Chad, a military source said.
"The Islamists fighters attacked early this morning and we returned fire and they were forced to flee back into Nigeria," the source told Reuters by telephone from Komguia, where the fighting took place.
Chadian President Idriss Deby earlier on Friday vowed to crush the insurgents who have killed thousands of people and threat the stability of the region.
"Chad will never bend in the face Boko Haram and I promise you that Boko Haram will disappear," he told a group of Muslim clerics.
Boko Haram has fought a six-year-old insurgency to carve out an Islamist state in northeast Nigeria and are carrying out cross-border attacks despite a military campaign involving Nigeria`s neighbours Niger, Cameroon and Chad.
Niger`s army killed at least 30 suspected fighters as it searched for militants in villages just over the border with Nigeria, Nigerien security sources said.
The army launched the operation on Thursday, a day after gunmen thought to be from Boko Haram crossed over from Nigeria and killed at least a dozen villagers on the Niger side of the border.
"Our defence forces who are engaged in the operation inside Nigeria between the towns of Malam Fatori and Damasak, killed the insurgents on Thursday," a security source said, requesting not to be named.
Boko Haram has started calling itself the Islamic State`s "West Africa Province" since pledging allegiance in March to the hardline militant group which controls large areas of Syria and Iraq.
Early on Friday, two suicide bombers, an elderly woman and a 10-year-old girl, killed at least nine people in the northeastern Nigerian city of Damaturu as worshippers gathered to mark the Muslim Eid al-Fitr holiday, a military spokesman said.
The group has targeted security forces, schools and other Muslim communities who do not share its hardline version of Islam.