The very powerful X-class solar flare of 2003 October 28 was detected with the INTEGRAL spectrometer as an intense gamma-ray flash of about 15 minutes. Despite the non-standard incidence of the solar gamma-rays, time-resolved spectra including several nuclear gamma-ray lines were obtained. Such a measurement with a high-energy-resolution instrument can provide valuable information of the isotopic abundances of the ambient solar material, as well as the composition, directionality and energy spectra of the accelerated nuclei. First results on the measured gamma-ray line ratios and time history of the neutron-capture line are presented.