Code to display links from tags is messing comments up

I’m using a piece of code to display the latest 10 posts from a certain tag in a post:

<ul>
 <?php
 global $post;
 $myposts = get_posts('numberposts=10&tag=tagname');
 foreach($myposts as $post) :
 ?>
    <li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
 <?php endforeach; ?>
</ul>

When I use it in a page it works fine and correctly displays the latest ten posts with the relevant tag.

But when I use it in a post although it correctly displays the latest posts it also interferes with the comments that are displayed below the post: it displays the comments from the last post described in the list.

I can’t work out what I’ve done wrong with the code – can anyone help please?

I’m using the Exec PHP plugin to execute PHP code in posts.