Rebels opposing the government in Chad say they have captured a town in the north-east of the country, inflicting heavy casualties on government forces.
The Union of Forces for Democracy and Development (UFDD) said its forces attacked the town of Ounianga Kebir at dawn on Saturday.
Chad's government disputed the rebel statement, playing down the clashes.
Chadian rebels launched a campaign last year aimed at overthrowing President Idriss Deby.
A spokesman for the rebels said the UFDD attacked as part of an effort to broaden the offensive against the government.
"We have been obliged to open several fronts," said Makaila Nguebla, from the Senegalese capital, Dakar.
"It is a military strategy, we are trying to generalise the conflict across the national territory so as to stretch the government forces."
Chad's Communication Minister, Hourmadji Moussa Doumgor, confirmed only that "some armed men" had briefly occupied Ounianga Kebir.
They then retreated towards the Sudanese border, the minister said.
The desert town of Ounianga Kebir lies about 900km (560 miles) north-east of Chad's capital N'Djamena.
The UFDD unsuccessfully tried to capture N'Djamena last April, with a coalition of rebel groups.
One of those groups (the United Front for Democratic Change) signed a peace accord with Mr Deby three weeks ago.
The UN says about 90,000 Chadians have been displaced by recent fighting.
The Chadian government has accused Sudan of backing the rebels - a charge Sudan denies - while Chad denies Sudanese claims that it supports black African rebels in Darfur.