MOSCOW, October 5. /TASS/. The Free Syrian Army and the moderate opposition in general remain a "phantom" group, Russian Foreign Minister Sergey Lavrov has said, adding that Moscow has called on the US to explain what it is and where it is based.

"No one has told us where the Free Syrian Army operates or where and how the other units of the moderate opposition act," Lavrov said.

"We will even be ready to establish contact with it, if these are indeed efficient armed groups of the patriotic opposition that consist of Syrians," the foreign minister added.

So far, the Free Syrian Army remains a "phantom group," he said. "Nothing is known about it," Lavrov said.

Lavrov said he has asked US Secretary of State John Kerry to provide information on this group and its leadership.

Last week, Kremlin spokesman Dmitry Peskov said "there is absolutely controversial information about this so-called army." "What is Free Syrian Army? Is this an official term? Are they official armed forces or what is it," Peskov said. He reiterated that Russia would support Syria in the fight against the Islamic State terrorist group and other extremists and terrorists.