ADEN, Yemen (AP) — Yemen's main southern city of Aden was shaken by double attacks Thursday, as a missile fired by rebels hit a military parade and suicide bombers blasted a police station. At least 51 people were killed in the deadliest day in nearly two years in the de facto capital of the U.S.- and Saudi-backed side in Yemen's civil war.

Most of the dead came from the missile strike, which slammed into a parade of newly graduated fighters belonging to a militia loyal to the United Arab Emirates, known as the Security Belt.

Among the dead was a senior commander in the militia, Monier al Yafi...