An international coalition of 100 aid and rights organizations has urged Western countries to stop selling arms to Saudi Arabia for its extensive air campaign against Iran-backed Shiite rebels in Yemen.

The Control Arms Coalition says the air campaign has caused heavy casualties. The group on Friday released a report listing 11 countries — including France, Britain, U.S. and Germany — that it says have sold arms such as drones, missiles and bombs worth $25 billion dollars in 2015 to the kingdom.

The report says the Saudi-led campaign in Yemen amounts to a "gross violations of human rights and possible war crimes."

The United Nations says the fighting in Yemen has killed more than 6,000 Yemenis since March 2015, and more than 35,000 have been wounded.