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>
    <images imcontinue="1|Flag_of_Croatia.svg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <images>
          <im ns="6" title="File:Flag of Albania.svg" />
          <im ns="6" title="File:Flag of Argentina.svg" />
          <im ns="6" title="File:Flag of Australia.svg" />
          <im ns="6" title="File:Flag of Austria.svg" />
          <im ns="6" title="File:Flag of Belarus.svg" />
          <im ns="6" title="File:Flag of Belgium.svg" />
          <im ns="6" title="File:Flag of Brazil.svg" />
          <im ns="6" title="File:Flag of Bulgaria.svg" />
          <im ns="6" title="File:Flag of Canada.svg" />
          <im ns="6" title="File:Flag of Chile.svg" />
        </images>
      </page>
    </pages>
  </query>
</api>