YEMENI security officials said a suicide attacker set off a massive car bomb in the southern city of Aden, killing 25 pro-government troops who had been preparing to travel to Saudi Arabia to fight in Yemen's northern border area.

They said the Monday attack left over 60 wounded, who have been taken to three area hospitals.

The men had been at a staging area near two schools and a mosque where they were registering to join the expedition, which the Saudis seek to build up to 5,000 men who will also receive training.

Yemen is in a civil war pitting the internationally recognized government and a Saudi-led coalition against the rebels and army units loyal to a former president. (AP)