UNITED NATIONS — Secretary-General Ban Ki-moon on Thursday called on the Syrian government to allow a U.N. team now in Damascus to swiftly investigate an alleged chemical weapon attack outside the capital that killed at least 100 people.
U.N. deputy spokesman Eduardo del Buey said Ban remains "deeply troubled" by the alleged attack on the eastern suburbs of Damascus on Wednesday and believe it needs to be investigated "without delay."
Syrian anti-government activists accused President Bashar Assad's regime of carrying out an attack using toxic gas and have reported death tolls ranging from 136 to 1,300. Even the lowest figure would make it the deadliest alleged chemical attack in Syria's 2 1/2-year civil war.
The government has denied that it used chemical weapons, calling the allegations "absolutely baseless."
Del Buey said the secretary-general "takes positive note" of the U.N. Security Council meeting Wednesday that backed his initial call for "a thorough, impartial and prompt investigation."
He said the secretary-general has been in touch with world leaders since Wednesday and is sending U.N. disarmament chief Angela Kane to Damascus to press for a U.N. investigation.
Under the terms of an agreement with Syria negotiated by Kane and chief weapons inspector Ake Sellstrom in July, the U.N. team can investigate three previous incidents of alleged chemical weapons use.
A new agreement would need to be negotiated for the 20-member team to be able to go to the Damascus suburb of Ghouta.
The U.N. team is scheduled to investigate an alleged chemical weapons attack that happened March 19 on the village of Khan al Assal outside the city of Aleppo, which was captured by the rebels last month. The government and rebels blame each other for the attack. The sites of the two other incidents to be investigated are being kept secret for security reasons.
More than 35 countries signed a letter to the secretary-general Wednesday requesting the U.N. experts to launch "an urgent investigation ... as expeditiously as possible" into Wednesday's incident as well.
Del Buey said the secretary-general is sending a formal request to the Syrian government to grant permission and access to the Ghouta area to the U.N. chemical weapons experts.
"He expects to receive a positive response without delay," del Buey said.
U.N. Deputy Secretary-General Jan Eliasson, who briefed the Security Council on Wednesday, expressed hope that the Syrian government will give the team access to the site as soon as possible, though he cautioned that because of fighting "the security situation right now does not allow such access."
"This represents, no matter what conclusions are, a serious escalation with grave humanitarian consequences and human consequences," Eliasson stressed.
The secretary-general reiterated his call for an immediate cessation of hostilities so that humanitarian assistance can be urgently delivered to the area of the latest incident, del Buey said.
U.S. State Department spokeswoman Jen Psaki said President Barack Obama has directed the U.S. intelligence community "to urgently gather additional information" on Wednesday's incident, saying the videos and photos "shock the conscience" and go "beyond the pale."
"At this time right now, we are unable to conclusively determine CW (chemical weapons) use, but we are focused every minute of every day since these events happened yesterday on doing everything possible within our power to nail down the facts," she said.
As part of this effort, she said, U.S. Secretary of State John Kerry has been coordinating and cooperation with his counterparts around the world.
Associated Press Writer Deb Riechmann contributed to this report from Washington