By Stephanie Hancock
BBC News, N'Djamena
Rebels intent on overthrowing Chad's president have attacked the border town of Adre in far-eastern Chad.
Rebels said a coalition of groups had launched the attack
A coalition of four rebel groups claims to control the town, after three hours of intense fighting, although they admit clashes are continuing.
Chad's government denies this and says those who launched the offensive have already been pushed back into Sudan.
The fighting has flared up in Chad, near the country's border with Sudan, after a few weeks of relative calm.
A spokesman for the United Forces for Democracy and Development (UFDD) told the BBC that four rebel groups had united for the offensive.
The rebels say they fully expect a counter-attack to be launched.
The Chadian government admits an offensive took place but is insisting the fighters have been forced back into Sudan.
Chad's defence minister claims that rebels were not responsible for the attack and, without elaborating, said it was Sudanese who had attacked the town.
He pointed out that Adre lies just 400m from the Sudan border and said it was inconceivable that Sudan had played no role in the attack.
Relations between Chad and Sudan have been deteriorating for some time and this latest attack will do nothing to ease the tension between the two countries.