It has described Sudanese President Omar Hassan al-Bashir as an "enemy of Chad".

"The Government calls on the Chadian people to mobilise against this Sudanese aggression," the Chadian statement said.

Foreign Minister Ahmat Allam-Mi says the Sudanese ambassador has been summoned to the ministry and given a memorandum listing "Sudan's aggressions against Chad".

Chadian rebels led two attacks against the town of Adre on its eastern border with Sudan on December 18.

Chad says its forces have repulsed the assaults, killing about 300 of the attackers, pursuing the rebels over the border into Sudan and destroying their bases there.

- Reuters