The prime minister of Chad has announced plans to send troops to its southern neighbour Central African Republic to fight rebels allegedly backed by Sudan.
Pascal Yoadimnadji, the prime minister, on Friday also called for the "general mobilisation" of Chad's people against what he called "a generalised war imposed by the Sudanese government".
He told Chad's National Assembly that "mercenaries in the pay of Sudan" had occupied several towns in northeast Central African Republic and were advancing west and south.
Humanitarian organisations say several thousand people in Bria, 600km northeast of the capital, have fled the rebel advance.
Yoadimnadji said Chad's government proposed sending troops to help its southern neighbour under a defence pact.
Ethnic violence
He said: "A popular saying goes that if your neighbour's house is on fire, you go to help him, or you risk the fire spreading to your house."
The prime minister added Chad had also suffered repeated incursions by "Sudanese soldiers" over its eastern border, triggering ethnic violence in Chadian communities which had killed more than 300 people in recent weeks.
At the start of the month, Idriss Deby Itno, the Chadian president and Francois Bozize, the president of CAR, accused Sudan of supporting the rebel movements fighting against them.
The Chadian head of state is one of the main supporters of General Bozize, who he helped take power in March 2003 by toppling former president Ange-Felix Patasse.
Sudan's government has repeatedly denied that it is backing rebels in Chad and Central African Republic.