Afghanistan, Asia, May 21 -- A top Russian security official has claimed that the Islamic State of Iraq and Syria (ISIS) terrorist group's offshoot in Afghanistan has amassed at least 5,000 fighters close to CIS border in North of Afghanistan.

The director of Russia's FSB Alexander Bortnikov made the remarks during a meeting with the ex-Soviet intelligence services in Dushanbe, according to Russia's RT Television network.

"Especially worrying is re-deployment of terrorist groups into northern provinces of Afghanistan," Bortnikov said.

He warned that 'Wilayat Khorasan', a local Islamic State affiliate, had managed to gather 5,000 fighters in the area.

A U.S. official had earlier told AFP that ISIS terrorists are heading to Afghanistan ...