Russia-owned Naftna Industrija Srbije (NIS) has halted crude processing as U.S. sanctions choke oil flows to Serbia, triggering fears of a fuel shortage ahead of winter. A shipment of roughly one million barrels of Kazakh KEBCO crude that arrived at Croatia’s Omisalj terminal on 9 October remains blocked after deliveries through the JANAF pipeline were suspended on 8 October, according to multiple industry sources cited by Reuters on Friday. The U.S. Treasury’s Office of Foreign Assets Control allowed a sanctions waiver on NIS…