Militants in Yemen fired on Saudi border troops in Saudi Arabia 's U.S. Navy 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 .
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 .