Analysis and simulations of fast particles produced by a high-intensity short laser pulse interacting with a foil target are performed. Initially, the plasma density distribution of the foil target has a smooth gradient with the scale length of plasma density varying across it. The absorbed laser energy is transferred to fast electrons, which penetrate in the foil and are partially ejected from the foil rear. These electrons produce an electric field that causes an ion beam to be emitted from the foil. We analyze the mechanism of ion acceleration in the foil plasma and the influence of the density gradient and other laser and plasma parameters on ion acceleration. The angular distributions of the ejected electrons and ions are calculated.