Mohammed bin Salman, the Saudi crown prince, has thrown his weight behind the Yemeni government as it battles against a separatist group backed by Saudi Arabia’s allies in the United Arab Emirates (UAE). The prince’s military coalition in Yemen fractured dramatically over the weekend as the Yemeni government and the southern separatists turned their guns on each other after years of fight side-by-side under Saudi leadership. The intense fighting in the port city of Aden left 40 people dead as separatist forces, who seek an independent state in south Yemen, seized control of government buildings and fought against presidential guards. Saudi jets carried out an airstrike in Aden in support of government troops and Prince Mohammed met with the Yemeni president, Abdrabbuh Mansur Hadi, on Sunday night in a show of support. Mr Hadi’s office said the two men discussed the separatist “coup” against the government and “various other crimes against the sons of Aden”. By Monday morning a tense calm appeared to have settled over Aden with no reports of fresh fighting between the two sides. Humanitarian groups warned that thousands of civilians were trapped in the firing line. Mohammed bin Salman is supporting the Yemeni government. Credit: REUTERS/Jorge Silva/File Photo But it was unclear how the standoff would be resolved and whether separatist forces, known as the Southern Transitional Council (STC), would withdraw from seized government buildings. Aidarus al-Zubaidi, the head of the STC, said he was committed to a ceasefire and was prepared to travel to Saudi Arabia to negotiate a long-term truce. He said his forces had moved against the Yemeni government because he had intelligence that government troops were preparing to launch an attack of their own. Even if the immediate crisis in Aden can be resolved, the violence highlights the deep fractures in Prince Mohammed’s coalition, which has been struggling for more than four years against Houthi rebels aligned with Iran. Saudi Arabia led an Arab military coalition into an air campaign against Houthi forces in 2015 in an effort to restore Mr Hadi’s control over Yemen. The fighting has plunged the country into famine and the UN now considers Yemen the world’s worst humanitarian crisis. Thousands of civilians have been killed by the Saudi-led coalition's airstrikes. The separatists are armed by the UAE Credit: REUTERS/Fawaz Salman The UAE, which has one of the region’s most effective militaries, played a major role in helping government forces push the Houthis back towards their stronghold in the country’s northwest. It also provided weapons and support to the STC, arguing that the separatists were key partners in fighting both the Houthis and jihadists groups in Yemen. However, the UAE withdrew most of its forces from Yemen in recent months, hampering the coalition’s ability to continue fighting the Houthis. With their patrons withdrawing from Yemen, the STC decided to move against the Yemeni government. In an statement over the weekend, the Yemeni embassy in Washington said it held “the United Arab Emirates fully responsible for the coup perpetrated against the state in Aden”.