N'DJAMENA, Chad (Reuters) -- Chad repulsed a rebel attack on a town near the Sudanese border on Sunday and blamed its neighbor for fighting that killed around 100 people.

Army deserters allied to a rebel group called the Rally for Democracy and Liberty (RDL) mounted the early morning attack in Adre, a few miles from the border, Chad's Communication Minister Hourmadji Moussa Doumgor said.

Chad accuses the RDL of being a "militia used by the Sudanese government".

"The Chadian government holds the Sudanese government totally responsible for this morning's attack mounted from its territory," Doumgor said in a statement.

But Sudanese Foreign Ministry spokesman Jamal Ibrahim denied Sudan was involved in the attack. "Sudan is not planning or doing anything against Chad," he said.

Chadian forces were still pursuing rebel elements on Chadian soil, but would chase them over the frontier into Sudan if necessary, Doumgor said.

"That would be justified," he said.

Doumgor told Reuters earlier that losses on the rebel side had been worse than on the government side.

The toll could not immediately be independently verified.

Aid workers on the Sudanese side of the border said the attack was the worst offensive to date of an escalating conflict. Earlier Sudanese rebels and aid workers reported hearing large explosions and heavy fighting near Adre.

Scores of Chadian soldiers deserted their barracks in late September before regrouping near the border, and the government has accused Sudan of using the deserters to fight rebels in Darfur and of backing Chadian rebel activities.

Sudanese army sources reported sporadic fighting in recent days, crossing over the long, porous border between the countries, but added the Sudanese army was not involved.

Both Darfuri rebels and aid workers in the region have reported large troop movements during the past two weeks near the border, with reports of Chadian troops patrolling on the Sudanese side of the border.

The deserters pose a threat to President Idriss Deby by demanding his resignation. They are also accused of attacks on army bases in the capital N'Djamena.

The clashes add to tensions in Darfur, which has been in open revolt for almost three years. One of the main Darfur rebel tribes, the Zaghawa, live on both sides of the border.