UNITED NATIONS (AP) — Secretary-General Ban Ki-moon said peacekeepers in Darfur are facing increasing threats from fighting in the vast western province and along the Chad-Sudan border, and from a spate of kidnappings.

In a report to the U.N. Security Council circulated Monday, the U.N. chief also criticized the failure of rebel groups in Darfur to unify their positions and start serious discussions with the government to resolve the 6 1/2-year conflict.

He said the joint United Nations-African Union force has made significant strides toward full deployment — with 14,638 of its authorized 19,555 military contingent on the ground at the end of October — and is now, "more than ever," focusing on its critical tasks of protecting civilians and facilitating the delivery of food and other humanitarian aid.

But Ban said there are still "serious challenges" and "increased threats.

He cited ongoing fighting between Sudanese government forces and rebels which put civilian lives at risk and demonstrate "that the parties have not made a full commitment to a political solution to the Darfur crisis.

Between July and October, Ban said, "serious security incidents also took place along the Chad-Sudan border" including clashes between the armed forces of both countries.

I again call on all parties to exercise restraint, to cease support for rebel groups in both Chad and the Sudan, and to work in good faith towards a secure environment in Darfur," he said.

The secretary-general welcomed a statement issued after a meeting between top government officials from both countries on Oct. 10-11 affirming their commitment to improve relations. He stressed that good relations between Sudan and Chad are the cornerstone for peace in Darfur.

In another major threat, Ban said four kidnappings in Darfur since March "represent an extremely alarming development for international staff in Darfur.

Two international staff members working for the U.N.-AU force, known as UNAMID, who were taken from their home on Aug. 29 are still being held while two international aid workers were released on Oct. 18 after 107 days in captivity. Another staff member for an international organization was abducted on Oct. 22, he said.

These incidents of hostage taking of international workers are a new and deeply troubling development in Darfur, with the potential to undermine the efforts of the international community," Ban said.

The security implications of these events have already led to the suspension of some activities by the humanitarian community," he said.

In addition to the kidnappings, Ban said members of UNAMID were also targeted on four occasions between July and October resulting in the death of one peacekeeper.

These incidents, as well as ambushes, carjackings and violent robberies of staff residences "underscore the extremely difficult and volatile conditions" in which UNAMID and humanitarian workers are working, he said.

Ban said the military activity and increased threats to international staff are affecting the freedom of movement for the U.N.-AU force and humanitarian workers. He said since January, there have been at least 42 instances where a UNAMID patrol was blocked by a government official.

The Darfur conflict began in February 2003 when ethnic African rebels took up arms against the Arab-dominated Sudanese government in Khartoum, claiming discrimination and neglect. Khartoum is accused of retaliating by arming local nomadic Arab tribes and unleashing militias known as the janjaweed on civilian populations — a charge the government denies.

U.N. officials say at least 300,000 people have lost their lives from violence, disease and displacement, and 2.7 million have been driven from their homes.