fatal error when importing XML: Class 'DOMDocument'

Hello there,

I wanted to move my wordpresssite – therefore I’ve exported my wordpressdata. When trying to import them – the following error occurs:

fatal error: Class ‘DOMDocument’ not found in /var/www/wordpress/wp-content/plugins/wordpress-importer/parsers.php on line 61

Does anyone know how to solve this problem?

I am happy to give more infos if required – unfortunately I don’t know where to start.

Thanks so much!