The production of phi mesons in the collisions of 2.83 GeV protons with C, Cu, Ag, and Au at forward angles has been measured via the phi -> K(+)K(-) decay using the COSY-ANKE magnetic spectrometer. The phi meson production cross section follows a target mass dependence of A(0.56 +/- 0.33) in the momentum region of 0.6-1.6 GeV/c. The comparison of the data with model calculations suggests that the in-medium phi width is about an order of magnitude larger than its free value. (C) 2010 Elsevier B.V. All rights reserved.