UNITED NATIONS - The United Nations will investigate attacks on UN-supported facilities in northwest Syria, Secretary-General Antonio Guterres announced on Thursday, two days after two-thirds of the Security Council pushed for such an inquiry.Britain, France, the United States, Germany, Belgium, Peru, Poland, Kuwait, the Dominican Republic and Indonesia delivered a demarche - a formal diplomatic petition - to Guterres on Tuesday over the lack of an inquiry into attacks on some 14 locations."The investigation will cover destruction of, or damage to facilities on the deconfliction list and UN-supported facilities in the area," UN spokesman Stephane Dujarric said in a statement, adding that it will "ascertain the facts of these incidents and report to the Secretary-General.""The Secretary-General urges all parties concerned to cooperate with the board once it has been established," Dujarric said.The locations of the UN supported facilities and other humanitarian sites like hospitals and health centers had been shared with the warring parties in a bid to protect them. However, the United Nations has questioned whether it made them a target.Syrian President Bashar al-Assad's forces, backed by Russia, began an offensive on the last major insurgent stronghold three months ago that the United Nations says has killed at least 450 civilians and displaced more than 440,000 people.Russia and Syria have said their forces are not targeting civilians or civilian infrastructure and questioned the sources used by the United Nations to verify attacks. Syria has also told the United Nations that more than a 100 sites "have been out of commission since being taken over by terrorist groups."An array of insurgents have a foothold in northwestern Syria. The most powerful is the jihadist Tahrir al-Sham, the latest incarnation of the former Nusra Front which was part of al Qaeda until 2016.The Security Council has been deadlocked on Syria with Russia and China - two of the body's five veto powers along with Britain, France and the United States - shielding Assad's government from any action during eight years of war.In 2014, former Secretary-General Ban Ki-moon set up a similar inquiry into attacks on UN facilities and the use of UN sites to store weapons during fighting between Israel and Hamas militants in the Gaza Strip.That inquiry found that Israel fired on seven UN schools during the 2014 Gaza war, killing 44 Palestinians who had sought shelter at some sites, while Palestinian militants hid weapons and launched attacks from several empty UN schools.