Npr-- This weekend's bloodshed broke out Sunday in the southern port city of Aden, where forces loyal to the separatist Southern Transitional Council traded gunfire with loyalists of  former President Abed Rabbo Mansour Hadi. The scattered fighting has claimed at least 12 lives and injured scores more.

The two sides had shared an uneasy alliance since 2014, when they were united in their opposition to the Houthi group who seized cities in the country's northwest, including the capital, Sanaa. Together, the STC and Hadi's forces managed to force the Houthis from Yemen's southern governates and Aden, the large city where Hadi's government had presided since its ouster from the capital.

The Associated Press reports Ahmed Obeid bin Daghir, prime minister in Hadi's government, described the violence Sunday as a "coup" — while STC senior official Ahmed Said Ben Brik cast his fellow separatists as reluctant warriors who broke out their weapons only when pressed.

"They forced us into military uniforms even though we said we are peaceful," he tweeted Sunday." But we are ready."

As Reuters notes, the fighting follows the expiration of a deadline set last week by the southern separatists. Irate at what they call corruption and the deep erosion of public services in the areas still governed by Hadi, the STC had delivered him an ultimatum: shake up the cabinet and sack bin Daghir or face ouster. That deadline came and went without sign that Hadi had any intention of complying.