UNITED NATIONS — The U.N. peacekeeping chief called on the government of Sudan on Tuesday to cooperate with the international chemical weapons watchdog in any investigation of alleged chemical weapons use in the Darfur region.

Herve Ladsous told the U.N. Security Council that peacekeepers from the U.N.-African Union force in Darfur have been denied access to the area in Jebel Marra where Amnesty International alleged that at least 30 chemical attacks have taken place since January.

“We were very much alarmed by the allegations,” Ladsous told reporters.

Sudan is a party to the Chemical Weapons Convention banning the use of toxic chemicals.

Sudan’s U.N. Mission said in an updated statement posted on its website Tuesday that the country does not possess chemical weapons and called the allegations “baseless and fabricated.”

It said Sudan’s military and civilian industrial facilities “are all open … any time” for visits by the Organization for the Prohibition of Chemical Weapons, which monitors implementation of the convention.

The OPCW said last week that it examined “the relevant parts” of the Amnesty International report and noted the government’s response. “Without further information and evidence being made available, it is not possible at this stage to draw any conclusions based on the content of the report,” an OPCW statement said.

Ladsous said the U.N. would therefore “encourage the government of Sudan … to maintain full cooperation with any future OPCW investigation as it has expressed readiness to do.”

While Sudan’s U.N. Mission gave a green light for the OPCW to visit industrial sites, it made no mention of an OPCW visit to Jebel Marra, a stronghold of a Sudan Liberation Army faction which is one of the main rebel groups fighting Sudanese security forces.

Ladsous said an upsurge in fighting in mid-September in Jebel Marra between government forces and fighters loyal to the Sudan Liberation Army’s founder Abdul Wahid Elnur has displaced at least 5,500 people, and possibly 16,000 according to some claims.

Secretary-General Ban Ki-moon said in his latest report that between January and late August over 80,000 people were newly displaced across Darfur, mainly in Jebel Marra. He said unverified reports offered a much higher figure for the number of newly displaced people in Darfur.

Darfur, a region in western Sudan which is the size of Spain, has been in turmoil since 2003, when ethnic Africans rebelled, accusing the Arab-dominated Sudanese government of discrimination and neglect. The United Nations says at least 300,000 people have died in the conflict and 2.7 million have fled their homes.

Ban reported “some progress” in various efforts to resolve the conflict, but Abdul Wahid Elnur isn’t part of negotiations and there have been no consultations with his leadership since July.

“We continue to engage both sides in the urgent need to resume dialogue,” Ladsous said.

Russia’s U.N. Ambassador Vitaly Churkin, the current Security Council president, cited diminished violence and “a lot of progress on the political track” in Darfur.

He said the council “needs to seriously contemplate putting some pressure” on opposition leaders who refuse to negotiate, hinting at sanctions.

Sudan’s U.N. Ambassador Omer Dahab Fadl Mohamed said government forces have pushed back against rebels everywhere except some pockets in Jebel Marra. There is “a great improvement on the security front,” he said, and more than 150,000 displaced people have returned to their villages.

Mohamed said “it is high time now” for the AU-UN mission known as UNAMID to start implementing an “exit strategy” by reducing troop levels in west, south and north Darfur.