Yemen's President Abed Rabbo Mansour Hadi arrived in the southern port city of Aden Tuesday following nearly six months of exile in Saudi Arabia, Hadi's arrival comes as troops supporting him are struggling to advance from the key battleground of Marib to the rebel-held capital some 165 kilometers (103 miles) to their west. Meanwhile, independent security officials said a Saudi-led coalition airstrike hit a hotel housing Shia Houthi rebels in Yemen's capital Sanaa, killing at least 25 people.

Arab coalition jets have strucked several cities across Yemen as relief organisations warn of a deteriorating humanitarian situation. Fighter jets targeted a Houthi-controlled arms depot in Fajj Attan, a neighbourhood overlooking the Yemeni capital Sanaa, residents said on Wednesday. Air strikes also severely damaged a Houthi rebel-controlled naval base in the province of al-Hudaydah on the Red Sea coast, residents said.

Warplanes from a Saudi-led military coalition conducted airstrikes Wednesday in the southwestern Yemeni city of Taiz, hours after Saudi officials had announced they were ending a nearly monthlong military operation against a rebel group in order to focus on a "political process." The warplanes bombed Houthi positions during heavy clashes in Taiz on Wednesday morning, according to a local official in the city.

Egypt said Thursday that it was prepared to send troops into Yemen as part of a Saudi-led campaign to drive back the Iranian-backed Houthi advance, signaling the growing likelihood of a protracted ground war on the tip of the Arabian Peninsula. A day after Saudi Arabia and a coalition of nine other states began hammering the Houthis with airstrikes and blockading the Yemeni coast, President Abdel Fattah el-Sisi of Egypt said in a statement that the country s navy and air force had joined the campaign and that its army was ready to send ground troops "if necessary."

Saudi Arabia has a long history of military intervention -- most of it harmful -- in what it considers its backyard, but the region had grown so used to Saudi Arabia's role as a player of proxy wars in Syria and Iraq that anything as decisive as direct military force seemed to hail from a bygone era. This time, the Houthis and Iran badly miscalculated. Riyadh's hand was forced for three reasons.

Warplanes have targeted the palace used by Yemen's President Abdrabbuh Mansour Hadi in the southern city of Aden. Officials said anti-aircraft guns prevented any direct hits on the hilltop compound. But witnesses saw smoke rising from the area afterwards. It is not clear if Mr Hadi was inside, but aides said he was now safe. Earlier, there were clashes at Aden's airport between troops and militiamen loyal to Mr Hadi and those backing his predecessor and the Houthi rebels.