Russia and China on Wednesday accused the United States and Britain of illegally attacking military sites used by Yemen’s Houthi rebels to launch missiles at commercial vessels in the Red Sea, disrupting global shipping.

U.S. deputy ambassador Robert Wood and UK Ambassador Barbara Woodward countered that the Houthi attacks are illegal, and their “proportionate and legal action” against the Yemen rebels are being taken in self-defense.

Woodward said the Houthi attacks are “driving up the costs of global shipping, including the costs of food supplies and humanitarian aid in the region.”

But Russia’s deputy U.N. ambassador Dmitry Polyansky and China’s U.N. envoy Zhang Jun argued that the U.N. Security Council never authorized military action against Yemen.