Saudi Arabia launched airstrikes early Tuesday on the Yemeni port city of Mukalla. The target was a weapons shipment from the United Arab Emirates destined for the UAE-backed Southern Transitional Council (STC). This attack sharply raised tensions between Saudi Arabia and the STC. According to Saudi state news, the strikes came after two ships from the UAE port of Fujairah arrived in Mukalla. Weapons were unloaded and seen as a threat to security. Saudi Arabia responded with a "limited military operation" to destroy the arms. The UAE has not commented on the bombing. Mukalla lies in Yemen’s Hadramout region, recently captured by the STC, which sits about 480 km northeast of Aden, the base for anti-Houthi forces. This comes a few days after Saudi airstrikes last Friday, seen by analysts as a warning to the STC to halt advances and withdraw from Hadramout and Mahra. The STC expelled the Saudi-backed National Shield Forces from these regions. Supporters of the STC are increasingly flying the flag of old South Yemen, a country that existed from 1967 to 1990. Demonstrations have pushed to restore that independence, increasing friction between Saudi Arabia and the UAE. Though Saudi Arabia and the UAE cooperate in OPEC, they compete for influence in Yemen and the Red Sea region. Their rivalry also extends to Sudan, where they back opposing sides in a conflict there.