The officer was shot in the chest by gunmen who opened fire from the back of a white van. This was later found abandoned close to the largely republican Bogside district, sparking off a major security operation there.
The injured officer was taken to a local hospital where her condition was described as serious but stable. The circumstances of the attack leave little room for doubt that the IRA's intention was to kill her. The last police officer killed in Northern Ireland died in the same city in a mortar attack in April 1994.
Republican sources yesterday continued to deny all knowledge of an IRA ceasefire some reporters have predicted.