Nairobi/N'Djamena - Rebels and government troops have clashed in the east of Chad, prompting the United Nations to say it would act to protect civilians. Fighting broke out in the region south of Goz Beida on Wednesday, forcing aid workers to be evacuated from refugee camps, government sources told the BBC.

So far, there is no information on casualties. However, the rebel group said Wednesday its goal was to reach the capital N'Djamena.

Chad on Tuesday accused Sudan of sending armed groups over the border just two days after the feuding countries signed a reconciliation agreement in Qatar.

Chad's Communications Minister Mahamat Hissene told state radio that Sudan had sent in two armoured columns while the "ink has yet to dry on the Doha accord."

Sudan quickly denied the allegation.

The two countries only resumed diplomatic ties in November after cutting them in May 2008. The neighbours have long accused each other of conducting proxy wars through rebel groups.

In May last year, Khartoum accused Chad of backing Darfuri insurgents who attacked the Sudanese capital. Chad countered by blaming Sudan for an earlier rebel attack on N'Djamena.

Chad and Sudan signed the agreement, brokered by Qatar and Libya, in Doha on Sunday.

UN Secretary General Ban Ki-moon said Wednesday that the peacekeeping mission in Chad and the Central African Republic, known as MINURCAT, would protect civilians.

"Any attempt at destabilization through violent means is unacceptable and reaffirms that MINURCAT will act within its mandate and capabilities to protect civilians threatened by armed elements," Ban said.

Ban called on Sudan and Chad to resolve their differences by diplomatic means. (dpa)