Sample Package.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
    <types>
                <members>Account-Account Layout</members>  
  <members>NameSpacePrefix__ObjectName__c-NameSpacePrefix__Transaction Layout</members>
        <name>Layout</name>
    </types>
    <types>
  <members>NameSpacePrefix__ObjectName__c</members>
        <name>CustomObject</name>
    </types>
 <version>33.0</version>
</Package>

Note:

Make sure that NameSpacePrefix is used Properly.