He said that four members of the Chadian security forces were killed and six wounded in the fighting, which took place on Sunday and Monday.
Chad's government says Bichara had threatened to fight against the corruption of the Islamic faith in Chad, which is a secular state but counts just over half of its population as Muslims.
Fighting broke out when government troops tried to break up a group listening to one of Bichara's sermons, the AFP news agency reported.
Bichara's followers had been armed with swords, spears and bows, according to officials.
Chad has suffered waves of violence over the last few years, including inter-ethnic clashes, as well as raids over the eastern border from Sudan by Janjawid fighters, and successive attacks by anti-government groups.