By Madjiasra Nako

N'DJAMENA (Reuters) - President Idriss Deby of Chad said on Wednesday he knew the whereabouts of Abubakar Shekau, the leader of the Nigerian militant group Boko Haram, and called on him to surrender or risk being killed.

Chad's army has waged a series of battles against Boko Haram as part of a cross-border military campaign and has re-taken territory the militant group held in northeastern Nigeria.

"‎Abubakar Shekau must surrender. We know where he is. If he doesn't give himself up he will suffer the same fate as his compatriots," he told a news conference after a regional meeting.

"He was in Dikwa two days ago. He managed to get away but we know where he is. It's in his interests to surrender," Deby said, referring to a town in northeastern Nigeria held by Boko Haram that fell to Chad's army earlier this week.

Nigeria's presidency declined to comment on Deby's remarks and a defense spokesman did not immediately respond to requests for comment.

Nigeria's military has said on at least three occasions it had killed Shekau, or a man claiming to be him. Each time the leader has resurfaced to issue a fresh jihadist video, one of numerous videos the group has made.

The Chadian army is considered one of the best in the region, backed by a strong air force. It first deployed to help Cameroon fend off Boko Haram and is now pressing southwest into Nigerian territory after capturing the border town of Gambaru last month.

Boko Haram, a Sunni militant group, has killed thousands of people in Nigeria during a six-year insurgency to carve out an Islamic caliphate. It has also staged a series of recent cross- border attacks into Chad, Cameroon and Niger.

On Wednesday, a bomb planted and remotely detonated by Boko Haram militants near the southeastern Niger town of Diffa killed two soldiers and wounded a third, Niger military sources said.

In a separate attack, armed men on a motorbike killed at least two people in Kerawa, in the Far North region of Cameroon, on Tuesday around 2 p.m. (1300 GMT), according to a Cameroon army officer who declined to be identified.

(Additional reporting by Abdoulaye Massalaki in Niamey, Sylvain Andzongo in Yaounde and Julia Payne and Felix Onuah in Abuja; Writing by Matthew Mpoke Bigg; Editing by Larry King)