Suspected militants from Nigerian Islamist group Boko Haram have kidnapped about 80 people and killed several others in a cross-border attack on villages in neighbouring Cameroon.
Army officials said many of those abducted were children aged between 10 and 15 years.
They said soldiers intervened and exchanged fire with the raiders for around two hours.
A police source said the cross-border attack had "left some people dead" without giving an exact toll, adding that the Cameroon army had "launched an operation" in the wake of the assault.
The kidnapping was the biggest in Cameroon by the Islamists who have staged a series of attacks in the country in recent months and escalated their bloody insurgency in their stronghold in north-eastern Nigeria.
The assault was launched after neighbouring Chad deployed troops to combat Boko Haram both in Cameroon and Nigeria.
In Nigeria, the Chadian troops are seeking to recapture the strategic city of Baga, on the shores of Lake Chad, which straddles the borders of Chad, Nigeria, Niger and Cameroon and which fell to the Islamists early this month.
Satellite pictures released by Amnesty International and Human Rights Watch showed widespread destruction with around 3,700 buildings in Baga and nearby Doron Baga damaged or destroyed.
Amnesty International said as many as 2,000 civilians may have been massacred, but Nigeria's army objected to the "sensational" claims and said the death toll in Baga was about 150.
Some 400 Chadian army vehicles arrived in the Cameroonian border town of Kousseri on Saturday, and Chadian president Idriss Deby said they were "operational" as of Sunday.
Boko Haram last Monday launched an offensive against a Cameroonian military base in Kolofata, also in the far north of the country, in which 143 "terrorists" and one Cameroonian soldier were killed, according to Cameroon.
Boko Haram seized control of many towns and villages in north-east Nigeria, and has begun threatening some of the country's neighbours.
