Saudi warplanes have been backing a coalition of their allies in southern Yemen as they try to take over the country, aiming to reinstall former President Hadi. Today, those troops and warplanes were moving against the port city of Zinjibar.

The troops never arrived, however, as the Saudi warplanes launched an airstrike which hit them, killing at least 20 of their own allies. At least three of the slain were said to be troops from the United Arab Emirates, whose ground troops were deployed earlier this month to nearby Aden.

This isn’t the first “friendly fire” incident by Saudi warplanes in the current war. Last month, they killed 12 allied fighters in Lahj Province, and wounded dozens of others. The loyalists were moving toward the city of Taiz, according to reports.

Such incidents are likely the result of the extremely loose firing restrictions the Saudi warplanes appear to be operating under, which is the same reason a large number of civilians have been killed throughout the war, as Saudi planes seem to attack anywhere and everywhere.