Yemeni President Abd-Rabbu Mansour Hadi landed in Aden on Tuesday, airport sources said, returning to the southern port city for the first time since he escaped to Saudi Arabia as Houthi fighters closed in six months ago.A government source said Hadi would spend the Muslim Eid al-Adha holiday in Aden and then fly to New York to deliver a speech at the United Nations. Last week, Prime Minister Khaled Bahah and seven ministers returned to Aden to take up residence in the city.An alliance of Arab states - mostly Yemen's wealthy Arabian Peninsula neighbours - intervened in the impoverished country's civil war in March with the aim of restoring Hadi, and have helped drive the Iranian-allied Houthi forces back from Aden.Gulf ground troops are now trying to push into Houthi strongholds in northern Yemen and in Sanaa, which the group seized a year ago. So far, they appear to have made few gains.Alliance warplanes bombed two houses in the capital Sanaa on Tuesday, killing at least 20 people, medics saidThe air attack came a day after similar raids killed around 50 people. "Two missiles hit the two houses in the Asbahi district in southern Sanaa, destroying them, killing 20 people and wounding others," a medic at the scene said.Saba, the Houthi-controlled state news agency, said 236 people have been killed in air strikes over the last four days. Medics reached by Reuters estimated the death toll was lower for some of the incidents mentioned in the report.A spokesman for the Saudi Defence Ministry said on Tuesday that two Saudi soldiers strayed into enemy territory in Yemen and are presumed to be in the hands of the Houthis."Two soldiers from the Saudi forces are missing after they lost their way inside Yemeni territory and the evidence points to them being alive and detained by the Houthi militias," Brigadier General Ahmed al-Asseri said in a statement.