About 16 people working for the United Nations have been abducted in Sudan's western Darfur region, a Sudanese official said Saturday.

The state minister for foreign affairs, Najeeb al-Kheir Abdul Wahab, said the government was communicating "with all sides." He gave no further details, and a U.N. official declined to comment on the report. Spokesmen for the rebels were unavailable for comment.

Rebels took up arms against the government in Darfur last year, accusing it of neglecting the remote area bordering Chad and of arming Arab militias to loot and burn villages, a charge the government denies.

The United Nations has warned of a humanitarian crisis in Darfur, where the conflict is believed to have killed about 10,000 people, displaced about 1 million and left several hundred thousand in danger of starvation. About 158,000 refugees have fled to Chad, where the U.N. agency for refugees says many are at risk of attack by militias, and malnutrition and disease are spreading.

On Wednesday, the government said humanitarian workers could enter Darfur after notifying officials, a change from rules set up in May that required first applying for travel authorization. The move was apparently part of Sudan's efforts to streamline humanitarian aid and a response to complaints of delays and lack of full cooperation from the government.

Separately, the government and rebels in the southern part of the country signed a declaration restating their commitment to a string of peace accords aimed at ending Africa's longest civil war.

Kenyan President Mwai Kibaki hosted the signing ceremony, which also launched the final phase of talks between Sudan's first vice president, Ali Uthman Muhammad Taha, and rebel leader John Garang to end 21 years of war.

Sudanese women in brightly patterned robes ululated as Taha and Garang signed the declaration, which covers six previous accords, the building blocks for a comprehensive peace deal.

"The document we have just signed . . . represents a solemn declaration on our part that war in Sudan is truly coming to an end," Garang said.

Before a gathering of foreign dignitaries, including Arab League Secretary General Amr Moussa and Egyptian Foreign Minister Ahmed Maher, Taha and Garang held aloft copies of the document in which both sides pledged to wrap up negotiations as quickly as possible.

"I would like to reiterate the determination of the government of Sudan to continue the peace process and implement all texts relating to this peace process," Taha said.

The negotiators are expected to nail down the remaining issues, including arrangements for a cease-fire and how to implement a final deal, when they resume talks on June 22. Mediators in Kenya, where talks are being held, have said a final deal could be concluded within two months.

The war is often depicted as a conflict between the Arab, Muslim north and the black animist and Christian south. The fighting has killed 2 million people in the south.