United Nations Secretary General Kofi Annan expressed great concern Tuesday over the recent upsurge in violence and instability in such conflict-torn African countries as the Democratic Republic of the Congo and Cote d'Ivoire.

"I am also greatly concerned by the recent upsurge in violence and human rights abuses in the eastern Democratic Republic of the Congo, by the continued instability in Cote d'Ivoire, and by the continued tension between this country, Ethiopia, and Eritrea," hesaid when addressing the opening of the third AU summit in Addis Ababa, capital of Ethiopia.

The UN chief urged for more efforts to end the various conflicts tearing the world's poorest continent apart.

"We must not let the achievements of recent years be rubbed out by a return to an Africa in which millions are plagued by terrible violence," he said. "We must work together to end the terrible conflicts that are disfiguring our continent."

Annan highlighted his concern over the situation in Darfur region of the Sudan, describing it as "horrific", and called on the international community to redouble its efforts to meet the urgent humanitarian needs of the people there.

"I am thinking, in particular, of the horrific situation in Darfur in western Sudan ... without action, the brutalities already inflicted on the civilian population of Darfur could be a prelude to even greater humanitarian catastrophe -- a catastrophe that could destabilize the region," he said.

He also urged the Sudanese government and rebel groups to work together to end the crisis in Darfur peacefully.

"I remind the government of its sacred duty to protect its citizens, and the rebel groups of their responsibility and duty to respect the ceasefire and work with the government to end the conflict peacefully," he said.