This paper proposes a new algorithm to address blind image super-resolution by fusing multiple blurred low-resolution (LR) images to render a high-resolution (HR) image. Conventional super-resolution (SR) image reconstruction algorithms assume either the blurring during the image formation process is negligible or the blurring function is known a priori. This assumption, however, is impractical as it is difficult to eliminate blurring completely in some applications or characterize the blurring function fully. In view of this, we present a new maximum a posteriori (MAP) estimation framework that performs joint blur identification and HR image reconstruction. An iterative scheme based on alternating minimization is developed to estimate the blur and HR image progressively. A blur prior that incorporates the soft parametric blur information and smoothness constraint is introduced in the proposed method. Experimental results show that the new method is effective in performing blind SR image reconstruction where there is limited information about the blurring function.