You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <backlinks blcontinue="0|Main_Page|98" />
  </query-continue>
  <query>
    <backlinks>
      <bl pageid="28" ns="0" title="Weapons" />
      <bl pageid="30" ns="0" title="Class 1 weapons" />
      <bl pageid="33" ns="0" title="IZHMASH Kalashnikov AK-74" />
      <bl pageid="50" ns="0" title="Accuracy International Arctic Warfare Super Magnum" />
      <bl pageid="53" ns="0" title="Alexander Arms Ulfberht" />
      <bl pageid="58" ns="0" title="Colt M16A4" />
      <bl pageid="61" ns="0" title="IZHMASH Kalashnikov AKMS" />
      <bl pageid="63" ns="0" title="IZHMASH Kalashnikov AKM" />
      <bl pageid="67" ns="0" title="Weapon accessories" />
      <bl pageid="71" ns="0" title="List of magazines" />
    </backlinks>
  </query>
</api>