WASHINGTON — The United States launched a military strike Thursday on a Syrian government target in response to their chemical weapons attack that killed dozens of civilians earlier in the week.

On President Donald Trump’s orders, U.S. warships launched 59 Tomahawk cruise missiles at a Syrian government airbase where the warplanes that carried out the chemical attacks were based, U.S. officials said.

The strike is the first direct military action the U.S. has taken against the regime of Syrian President Bashar al-Assad in the country’s six-year civil war and represents a substantial escalation of the U.S. military campaign in the region, which could be interpreted by the Syrian government as an act of war.

Six people were killed in the airstrike, according to a televised statement by the Syrian’s Armed Forces General Command.

The governor of Homs Talal al-Barzai tells Lebanon’s Al-Mayadeen news channel that five people were killed and seven wounded in the missile strike, and that civilians living in the village neighboring the base were among the casualties, according to reporting by Russia’s state-run RIA news agency.

Additionally, the U.K.-based Syrian Observatory for Human Rights says that four Syrian regime officers were killed in the strike on the Shayrat Airbase in Homs province on Friday.

According to SOHR Director Rami Abdulrahman, two sources from inside the airbase including a regime officer confirmed the fatalities.

“Tonight, I ordered a targeted military strike on the air field in Syria from where the chemical attack was launched,” Trump said during short remarks to reporters at Mar-a-Lago, where he ordered the strike just hours earlier. “It is in this vital national security of the United States to prevent and deter the spread and use of deadly chemical weapons.

There can be no dispute that Syria used banned chemical weapons, violated its obligations under the Chemical Weapons Convention and ignored the urging of the U.N. Security Council. Years of previous attempts at changing Assad’s behavior have all failed and failed very dramatically.”

Shift in policy

Trump’s decision marked a dramatic shift in his position on whether the U.S. should take military action against the Syrian president’s regime — which Trump opposed during his campaign for president — and came after the president was visibly and publicly moved by the images of this week’s chemical weapons attack.

The strike took place at 6:40 p.m. MDT (3:40 a.m. local time), when there would be minimal activity at the base, and targeted aircraft, hardened aircraft shelters, petroleum and logistical storage, ammunition supply bunkers, air defense systems, and “the things that make the airfield operate,” Pentagon spokesman Capt. Jeff Davis told reporters.

The missiles were launched from warships in the eastern Mediterranean.

“Initial indications are that this strike has severely damaged or destroyed Syrian aircraft and support infrastructure and equipment at Shayrat Airfield, reducing the Syrian Government’s ability to deliver chemical weapons,” the Pentagon said in a statement.

Briefing reporters late Thursday night, Secretary of State Rex Tillerson said the strike did not represent a “change in our policy or our posture in Syria,” even though the Thursday night strike marked the first time the U.S. had decided to take military action against the Syrian government.

“There has been no change in that status,” he said. “It does demonstrate that President Trump is willing to act when governments and actors cross the line … and cross the line in the most heinous of ways.”

Tillerson said the administration felt the strike was “proportional because it was targeted at the facility that delivered this most recent chemical attack.”

The U.S. military also showed reporters Thursday night an image of the radar track of a Syrian airplane leaving the airfield and flying to the chemical strike area Tuesday. A second image of bomb damage craters at the airbase was also shown to reporters at the Pentagon.

Tillerson said the U.S. has a “very high level of confidence” that the Syrian regime carried out at least three attacks in recent weeks — including on Tuesday — using Sarin and nerve gas.

The strikes represented not only an escalation of the U.S. role in Syria, but could have a ripple effect on the U.S.’ relations with the Syrian regime’s powerful backer, Russia.

Russians were present at the base the U.S. struck Thursday night, a U.S. defense official said, though the role of those Russians was not immediately known.

Tillerson confirmed that the U.S. military contacted their Russian counterparts about the attack ahead of time, in accordance with deconfliction policies between the U.S. and Russia over military activities in Syria.

A Russian official said the strike will undermine the war on terror and warned they may halt cooperation with U.S. forces.

“Russia will demand an urgent U.N. Security Council meeting after the U.S. airstrike on a Syrian aviation base,” said Viktor Ozerov, head of the Russian Federation Council’s defense committee, according to state news agency RIA.

“This is an act of aggression against a UN member,” Ozerov said. “Cooperation between the Russian and U.S. militaries may be shut down after the U.S. strike.”

Congressional reaction

Lawmakers generally supported Trump’s decision to strike back against Assad, but cautioned the president against unilaterally starting a war without first consulting Congress.

A pair of defense hawks — Sens. John McCain and Lindsey Graham — who have frequently been critical of Trump, roundly praised his decision.

“Acting on the orders of their commander-in-chief, they have sent an important message the United States will no longer stand idly by as Assad, aided and abetted by Putin’s Russia, slaughters innocent Syrians with chemical weapons and barrel bombs,” McCain and Graham said in a joint statement.

But Sen. Rand Paul called on Trump to consult on Congress.

“While we all condemn the atrocities in Syria, the United States was not attacked,” Paul said. “The president needs congressional authorization for military action as required by the Constitution, and I call on him to come to Congress for a proper debate.”

The U.S. began launching airstrikes in Syria in September 2014 under President Barack Obama as part of its coalition campaign against ISIS, but has only targeted the terrorist group and not Syrian government forces.