A relatively efficient catalytic system containing elemental sulfur-ionic liquid was developed for the carbonylation of nitroaromatics and corresponding aromatic amines with carbon monoxide to give symmetric diarylureas in yields up to 96%. Additionally, unsymmetical urea N-phenyl-N'-(piperidine) urea was obtained in 70% yield in this catalytic system. (c) 2006 Elsevier B.V. All rights reserved.