Amnesty International is calling on the U.N. Security Council to take action over reports that the Sudanese government has used chemical weapons in Darfur.

The British-based human rights group released a report Thursday detailing at least 30 chemical attacks they say took place in the Jebel Marra area over the past eight months. Amnesty estimates that chemical weapons may have killed some 200 to 250 people, with many or most being children.

"The world cannot stand idly by any longer. The U.N. needs to act. A cloud of suspicion hangs over the Sudanese authorities' conduct in Darfur," said Tirana Hassan, adding the alleged attacks have "every sign of being a war crime."

U.N. spokesman Stephane Dujarric said the world body was "extremely and particularly concerned" by the report.