Islamic State supporters from Indonesia are traveling to join forces with their counterparts in the Philippines, raising concerns about cross-border violence, Indonesian anti-terrorism officials said on Tuesday.  Authorities in Southeast Asia have been on heightened alert since a gun-and-bomb attack rocked the Indonesian capital Jakarta in January and stamped Islamic State's presence in the region for the first time.

"Some (Indonesian Islamic State supporters) are training in the Philippines," said A. Syamsu of the Indonesian counter-terrorism agency. "There's no exact number yet but it could be dozens."  Authorities across the region have in the last year cracked down on Islamic State sympathizers attempting to travel to Syria.

Read more: Reuters