US congressman: Chechen extremist behind Istanbul attack

ISTANBUL (AP) — A Chechen extremist masterminded the triple suicide bombing at Istanbul's busiest airport that killed at least 44 people, a U.S. congressman has said.

Turkey's interior minister said the explosives used were a mix of RDX, TNT and PETN that were "manufactured," which chemist and explosives expert at University of Rhode Island, Jimmie Oxley, described as being military-grade, raising the question of how the attackers obtained the bombs.

A key partner in the U.S.-led coalition against the Islamic State group, Turkey also faces security threats from the Kurdish rebels who are demanding greater autonomy in Turkey's southeast region and from ultra-left radicals.

Kurdish rebels have carried out numerous car bomb attacks in the past year, including an attack Feb. 17 in Ankara that killed 39 people, and another devastating bombing in the capital in March.