Sudanese President Omar Hassan al-Bashir has accused Amnesty International of “lying” after the advocacy right group reported its forces had used chemical attacks against its civilians in Darfur.

Last month, Amnesty International accused Sudan’s government of carrying out at least 30 likely chemical weapons attacks in the Jebel Marra area of Darfur since January using what two experts concluded was a probable blister agent.

The rights group estimated that up to 250 people may have died as a result of exposure to the chemical weapons agents.

The most recent attack occurred on Sept. 9 and Amnesty said its investigation was based on satellite imagery, more than 200 interviews and expert analysis of images showing injuries.

But in his first reaction to the report, President Bashir denied the charges on Saturday.

“In the last few days, you have heard all the lies and allegations by Amnesty International on the use of chemical weapons,” Bashir said in a speech to members of his party.

“These are just pure lies”, he maintained.

The Amnesty report includes images of children suffering from chemical burns, satellite images of destroyed villages and displaced persons, extracts of interviews with more than 200 survivors and expert analysis in chemical weapons.

The OPCW (Organisation for the Prohibition of Chemical Weapons, a UN agency) has said it would need more information and evidence for a formal investigation, while a top UN official called for Sudan in early October to help shed light on the accusations.

Darfur has been the scene of a bloody conflict since 2003, when rebels from ethnic minorities took up arms against the government in Khartoum. President Bashir then launched a violent insurgency against the groups.

Since then, the UN estimates that the fighting has left at least 300,000 dead and 2.5 million displaced.

Bashir, sought by the International Criminal Court on charges of war crimes, crimes against humanity and genocide in Darfur, had solemnly announced in early September that peace had been restored in the region.