A Houthi strike on King Khalid International Airport in Riyadh killed at least 12 people and injured more than 300 on Saturday. The missile attack marks the deadliest incident on Saudi soil in more than a decade.

The Saudi-led coalition fighting the Houthis in Yemen condemned the strike and labeled it a ‘war crime’. Coalition officials pledged a firm response to the assault on the capital’s main transportation hub.

International condemnation followed quickly. The United Nations, Qatar, Pakistan, Canada, and other nations issued statements denouncing the attack on civilian infrastructure.

The Saudi-led coalition has been backing Yemeni government forces against Houthi militants for years. The assault on Riyadh’s main airport marks the most severe attack on the kingdom in over ten years.