The Southern Giants Brigades have sent military reinforcements to Yemen’s Al-Mudharabah and Ras Al-Arah districts in Lahj governorate after Houthi forces advanced into several areas near the border with Taiz, Yemeni military sources said on Sunday.

The reinforcements were deployed to the Al-Sabihah front, where local fighters have been involved in clashes with the Houthis. Reports from the area said fighting had intensified along the Taiz-Lahj border following the Houthi advance.

Yemeni sources said government-aligned forces and local tribes had retaken some positions that had fallen to the Houthis in the border areas, while clashes continued around Al-Mudharabah, Ras Al-Arah and the Kahboub mountain front overlooking the Bab Al-Mandab Strait.

The fighting is part of a wider escalation along Yemen’s western and southern fronts. Military sources have reported clashes around Taiz, Lahj and Bab Al-Mandab, while the Houthis have sought to strengthen their positions near the strategic waterway. Satellite analysis cited by the Institute for the Study of War found that Houthi forces had constructed defensive earthworks along parts of their frontline in Lahj earlier this month.

The latest fighting comes as the Houthis have expanded their military activity beyond Yemen's internal front lines. On Saturday, the group claimed attacks on targets in Saudi Arabia, including Riyadh, while Saudi authorities said they intercepted a ballistic missile launched towards the capital. No casualties were immediately reported from the intercepted missile.

The United States subsequently warned that hostilities involving Saudi Arabia and the Houthis could escalate rapidly. The State Department urged Americans in the Middle East to exercise increased caution and those outside the region to reconsider travel to or through the area.

US President Donald Trump also cut short a planned weekend at Camp David and returned to Washington on Saturday. The White House did not immediately provide a reason for the change, which came as fighting between Saudi Arabia and the Houthis intensified.

The renewed fighting is also adding to Yemen's humanitarian crisis. The International Organization for Migration said at least 112,000 people had been displaced inside Yemen amid the recent escalation, while nearly 3,000 others had crossed the Gulf of Aden to Djibouti by sea.