Rome prosecutors have opened an investigation into alleged abduction after the Israeli authorities intercepted 22 boats of Global Sumud Flotilla in international waters close to Crete last week while they were sailing towards Gaza to take aid there, sources said Monday.     Israel said it removed 175 activists from the boats.     Most, including 24 Italians, were subsequently released but two, Spanish national Saif Abu Keshek and Brazilian Thiago Avila, were arrested and taken to the Israeli