The U.S. military believes at least 1,000 jihadist fighters have been inspired to leave their homes in Asia to fight with militant groups across the battlefields of Iraq and Syria.

“Our estimations today is there’s probably been about 1,000 potential aspiring fighters that have moved from this region, based on kind of our overall assessment,” Admiral Samuel Locklear, the U.S. Pacific Command commander, told reporters at the Pentagon on Thursday.

“That number could get larger as we go forward, but certainly that’s about the size or the magnitude that we perceive at this point in time.”

The Asia-Pacific is currently home to myriad homegrown jihadist networks, from restive enclaves in the Philippines and Indonesia to the rough tribal highlands of Pakistan and Afghanistan.

…“All these attacks, the masterminds were Afghan veterans,” Rohan Gunaratna, head of the International Centre for Political Violence and Terrorism Research at Nanyang Technological University in Singapore, tells TIME.