Basque separatist group <a href="https://en.wikipedia.org/wiki/ETA_(separatist_group)" id="mw2w" rel="mw:WikiLink" title="ETA (separatist group)">ETA</a> commits one of its <a class="mw-redirect" href="https://en.wikipedia.org/wiki/1987_Hipercor_bombing" id="mw3A" rel="mw:WikiLink" title="1987 Hipercor bombing">most violent attacks</a>, in which a bomb is set off in a supermarket, <a href="https://en.wikipedia.org/wiki/Hipercor" id="mw3Q" rel="mw:WikiLink" title="Hipercor">Hipercor</a>, killing 21 and injuring 45.