UNITED NATIONS - A Saudi Arabia-led military coalition has asked the United Nations to reveal its sources of information that led the world body to briefly blacklist the kingdom for killing children in Yemen and invited UN experts to come to Riyadh.

The demand was included in a letter from Saudi Ambassador Abdallah Al-Mouallimi to UN Secretary-General Ban Ki-moon on the coalition’s behalf dated June 8.

The United Nations initially added the coalition to its annual child rights blacklist but removed it shortly afterward pending a review by the coalition and the United Nations in the face of protests from the Saudis and other Muslim nations.

Both Saudi Arabia and the United Nations have come under criticism after the UN chief admitted last week that he had removed Saudi-led coalition from the blacklist under “undue pressure.”

On Wednesday, UN spokesman Stephane Dujarric said that it is “paramount” to protect sources of information used in any UN report, especially in a conflict area. Therefore, he said, the UN will refuse a request from the coalition for sources used for the Yemen section of the Secretary-General’s annual report on children and armed conflict.

According to the Children and Armed Conflict (CAAC) report, Saudi Arabia was responsible for 60 percent of the 510 children killed and 667 others injured in Yemen last year.

Saudi Arabia launched its military aggression against Yemen in March last year in a bid to bring Abd Rabbuh Mansur Hadi back to power and crush the Houthi movement.

The CAAC report said the Saudi military conducted half of its aerial attacks against schools and medical facilities.

A week after publishing the report, Ban said he had decided to temporarily take Saudi Arabia off the blacklist after the kingdom and its allies threatened to cut off funding to UN programmes.

The Saudi ambassador to the UN has declared that the changes were “final and unconditional” and that Riyadh had been “vindicated.”

The announcement sparked international outcry and 20 prominent human rights groups urged the UN chief to put Riyadh back on the blacklist.

In a letter, signed by Human Rights Watch, Amnesty International and Oxfam among others, the rights groups accused Ban of giving in to “political manipulation” by the oil-rich kingdom.

Dujarric, the secretary-general’s spokesman,  said Saudi Arabia had invited a UN team to Riyadh for talks. “We’re studying it. We obviously remain interested in what information the Saudi-led coalition could provide us,” he said.

But Dujarric said “our preference” would be to hold meetings at UN headquarters in New York.

More than 9,400 people have been killed and at least 16,000 others injured since Saudi Arabia began its offensive on Yemen.