Sanaa , Yemen ( CNN ) A border guard was killed in a cross-boundary fire exchange with militants in Yemen this week , the state-run Saudi Press Agency reported Thursday -- marking Saudi Arabia 's first publicly known military death since it launched airstrikes against rebels inside its southern neighbor . The clash occurred Wednesday night at the border in southwestern Saudi Arabia 's Asir region , when militants in a mountainous area on the Yemeni side fired on Saudi border troops , prompting them to return fire , SPA reported . Besides the slain border guard -- identified as Cpl . Salman Ali Yahya al-Maliki -- 10 others suffered injuries that were not life-threatening , the Saudi media outlet said . On Thursday , Houthi rebels seized the presidential palace in the southern Yemeni port city of Aden , a neutral security official and two Houthi commanders in Aden told CNN . The palace had been where President Abdu Rabu Mansour Hadi , who fled the country last month , had stayed for a period of time after Houthis secured control of the capital , Sanaa , in January . According to the security official , Houthis now control most large districts in Aden amid ongoing clashes . Yemeni special forces , considered pro-Houthi and loyal to former President Ali Abdullah Saleh , arrived in Aden on Thursday in an attempt `` to secure the city , '' a Saudi official with knowledge of the situation told CNN . `` I can now confirm that it is not Saudi special forces who have landed but Yemeni special forces loyal to Saleh who landed by small boat . They are few in number and have made their way to the old parliament building , '' the intelligence official said . U.S. Navy warships , meanwhile , were patrolling off Yemen in search of suspicious shipping in the region , in particular any weapons shipments from Iran to the Houthi rebels they are supporting in Yemen , a U.S. defense official told CNN . The Navy on Wednesday came across a Panamanian-registered cargo ship that had left an Iranian port , the official said . Based on the route of the ship from Iran to Yemen , the Navy declared it a `` vessel of interest '' and requested permission from the captain to search it . The ship was found to be carrying cement and construction materials , the official said . It was sent on its way . The offshore area has been a route for weapons smuggling into Yemen , as well as Sudan and Gaza , so the Navy has maintained a regular surveillance presence there . The official said that increased fighting in the last several days in southern Yemen has resulted in other ships trying to dock to help civilians leave the country . Marie Claire Feghali , an International Committee of the Red Cross spokeswoman in Sanaa , described events in Aden as `` extremely fluid and very , very complicated . '' `` Hospitals are still struggling , running out of supplies . So are we , '' she said . `` We can not move much in Aden due to the intense fighting and chaos . '' A hospital near heavy fighting was forced to shut down . Officials : Al Qaeda fighters free 270 from Yemeni prisons . CNN 's Barbara Starr contributed to this report .
Militants in Yemen fired on Saudi border troops in Saudi Arabia 's Asir region , media outlet says . Rebels have taken Yemen 's presidential palace in Aden , sources say . U.S. warships are patrolling off Yemen in search of suspicious shipping , a U.S. defense official says .