WATCH: U.S. pledges ‘action’ after drone attack on Kyiv

The Biden administration said it “will not hesitate to use sanctions or take actions against perpetrators,” after waves of explosives-laden suicide drones struck Ukraine’s capital Monday.

Watch the briefing in the player above.

The concentrated use of the drones sowed terror and frayed nerves as blasts rocked the city. Energy facilities were struck and one drone largely collapsed a residential building, killing four people, authorities said.

Ukrainian Foreign Minister Dmytro Kuleba called for European Union sanctions on Iran for providing drones to Russia and reiterated Ukraine’s need for air defenses and ammunition.

In Washington, the State Department called Iran’s supply of deadly drones to Russia a violation of international law.

“Our French and British allies publicly offered the assessment that Iran’s supply of these UAV to Russia is a violation of U.N. Security Council Resolution 2231. And this is something that we agree with,” said Vedant Patel, the spokesman at Monday’s State Department briefing.

“We’re going to continue to surge unprecedented security assistance to Ukraine, including air defense, and as well as working with our allies to transfer air defense systems and other security assets for Ukraine to use,” Patel said.

READ MORE: Biden says nuclear ‘Armageddon’ at highest risk since Cuban Missile Crisis

In a second matter, The State Department also weighed in on the conflict in Ethiopia after U.N. Secretary-General Antonio Guterres demanded an immediate end to hostilities in Ethiopia’s northern Tigray region.

Guterres demanded the withdrawal of Eritrean forces fighting alongside the government, saying “violence and destruction have reached alarming levels” and “civilians are paying a horrific price.”

He called for an urgent resumption of talks between the two sides and said, “The United Nations is ready to support the African Union in every possible way to end this nightmare for the Ethiopian people.”

“We call on the Ethiopian National Defense Forces and the Eritrean Defense Forces to immediately halt their joint military offensive and for Eritrea to withdraw its forces from northern Ethiopia,” Patel said.

The warring parties had said they were ready to participate in AU-led talks which were due to take place in South Africa earlier this month, but they were postponed because of logistical and technical issues.