By Michelle Nichols

UNITED NATIONS (Reuters) - The United Nations Security Council will meet on Syria behind closed-doors on Thursday, diplomats said, after Turkey launched a military operation against Kurdish fighters in the northeast of the country.

The discussion of the situation in Syria by the 15-member Security Council was requested by the five European members, Britain, France, Germany, Belgium and Poland, diplomats said.

Turkish President Tayyip Erdogan, announcing the start of the military action on Wednesday, said the aim was to eliminate what he called a "terror corridor" on Turkey's southern border.

The move came just days after U.S. troops pulled back from the area.

United Nations Secretary-General Antonio Guterres is "very concerned" by the recent developments in northeast Syria and "any military operation must fully respect the U.N. Charter and international humanitarian law," U.N. spokesman Farhan Haq said.

"Civilians and civilian infrastructure should be protected," Haq said. "The secretary-general believes that there's no military solution to the Syrian conflict."

(Reporting by Michelle Nichols; Editing by Bernadette Baum)