DUBAI, United Arab Emirates — Saudi Arabia bombed Yemen's port city of Mukalla on Tuesday over what it described as a shipment of weapons for a separatist force there that arrived from the United Arab Emirates. The kingdom later directly linked the UAE to the separatists' recent advances in Yemen and warned Abu Dhabi its actions were “extremely dangerous.” The attack signals a new escalation in tensions between the kingdom and the separatist forces of the Southern Transitional Council, which is backed by the Emirates. It also further strains ties between Riyadh and Abu Dhabi , which had been backing competing sides in Yemen’s decadelong war against the Iranian-backed Houthi rebels amid a moment of unease across the wider Red Sea region . The two nations, while closely aligned on many issues in the wider Mideast, increasingly have competed with each other over economic issues and the region's politics. Yemen’s anti-Houthi forces later declared a state of emergency Tuesday, ending its cooperation with the UAE and ordering all Emirati forces within its territory to evacuate withi