Positioning labels in FOP

I want to position label-text in the left margin of the page at the left of the containing paragraph:

XML example:
<para>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor <label>This is a label</label>incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</para>

Page example:
+------------------------------+
|                              |
|        Xxxx xxxxx xxxxx xx   |
| label  xxxxxx xxxx xx xxxxx x|
|        xxx xx xxxxx xxx xxx  |
|        xxxx xx xxxxx.        |
|                              |
+------------------------------+


In HTML/CSS this is simple with labels marked with <span>:
span {
    display : block;
    width : 11em;
    position : absolute;
    left : 0.5em;
}

How can I get this in XSL?
Is this possible with FOP?