The Kremlin condemned Thursday’s military strike by the United States on an airbase in Syria, saying the action significantly harmed U.S.-Russian relations and were conducted under a “made-up pretext.”

Dmitry Peskov, a spokesman for Russian President Vladimir Putin, called the attack an “aggression against a sovereign state in violation of international law.” He was also quoted as saying the country did not believe Syria had chemical weapons, Reuters and the Russian-sponsored news network RT reported.

Russia also indicated it would help Syria strengthen its air defenses in response to the U.S. action.

The U.S. launched the strike, its first direct assault against the Syrian government, in response to a Tuesday chemical weapon attack allegedly carried out by Syrian President Bashar Assad’s forces. The chemical attack left at least 70 dead, including children.

“Assad choked out the lives of helpless men, women and children,” Trump told reporters at his Mar-a-Lago resort in Florida. “Even beautiful babies were cruelly murdered at this very barbaric attack. No child of God should ever suffer such horror.”

Pentagon officials said Russia was informed before the attack, but Secretary of State Rex Tillerson said the U.S. “sought no approval from Moscow” ahead of the initiative, Reuters reported.

“Russian forces were notified in advance of the strike using the established deconfliction line,” Capt. Jeff Davis, a Pentagon spokesman, said in a statement to reporters. “U.S. military planners took precautions to minimize risk to Russian or Syrian personnel located at the airfield.”

“The use of chemical weapons against innocent people will not be tolerated,” Davis added.

Early Friday, Russia called for an emergency meeting of the U.N. Security Council to discuss missile strike.

“This is not the first time the United States has resorted to such a thoughtless step, which merely exacerbates existing problems and threatens global security,” the ministry stated, per Reuters.

The Russian Foreign Ministry also announced it was suspending a Syrian air safety agreement with the U.S.

Russia has been a longtime ally of Assad, but became an entrenched part of the Syrian civil war after launching a large-scale air campaign in support of Assad-allied forces in September 2015. Russia’s airstrikes were a decisive turning point for the Syrian strongman, whose hold on the country had become increasingly imperiled that year amid rebel advances.

In the wake of Tuesday’s chemical weapon attack, Russia stood by its ally and denied that forces loyal to Assad carried it out. Instead, Moscow claimed that rebel forces in the country’s Idlib province were storing the gas and that it was released in an airstrike. International experts refuted that assessment.

The Kremlin on Wednesday also objected to a draft United Nations Security Council proposal brought by the United States, France and Britain calling for action in the wake of the chemical attack. In response, U.S. Ambassador to the United Nations Nikki Haley suggested that the White House could take unilateral action.

Nick Robins-Early contributed reporting.