(Recasts; adds details from U.N. Security Council)
By Michelle Nichols
UNITED NATIONS, June 18 (Reuters) - U.N. chief Antonio Guterres appealed to Russia and Turkey on Tuesday to stabilize northwest Syria as the U.N. aid chief said that some hospitals were not sharing their locations with the warring parties because that "paints a target on their back."
Russia, which supports Syrian President Bashar al-Assad in his country's civil war, and Turkey, long a backer of rebels, co-sponsored a de-escalation pact for the area that has been in place since last year.
But the deal has faltered in recent months, forcing hundreds of thousands of civilians to flee. Idlib in northwest Syria is the last remaining bastion of anti-government rebels after eight years of civil war.
"I am deeply concerned about the escalation of the fighting in Idlib, and the situation is especially dangerous given the involvement of an increased number of actors," Guterres told reporters, appealing to Russia and Turkey "to stabilize the situation without delay."
U.N. aid chief Mark Lowcock told the U.N. Security Council later on Tuesday that since late April the World Health Organization had confirmed 26 incidents affecting healthcare facilities in northwest Syria. He said two of the facilities were located in areas controlled by the Syrian government.
"Hitting a facility whose coordinates were shared as part of the U.N.'s deconfliction system is simply intolerable," he said. "A number of partners now feel that supplying geographical coordinates to be given to the warring parties effectively paints a target on their backs."
"Some have drawn the conclusion that hospital bombings are a deliberate tactic aimed at terrorizing people," Lowcock said.
He said the United Nations was reconsidering its deconfliction system and would inform the Security Council next week of its conclusions.
Russia and Syria questioned the sources of the U.N. information.
"We decisively reject any accusation of indiscriminate strikes. We're not carrying out attacks on civilians," . Russian U.N. Ambassador Vassily Nebenzia said.
Syrian U.N. Ambassador Bashar Ja'afari added: "Syrians and allies do not target schools or hospitals."
(Reporting by Michelle Nichols; Editing by Cynthia Osterman)
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