The United States launched dozens of cruise missiles Thursday night at a Syrian airfield in response to what it believes was Syria's use of banned chemical weapons that killed at least 100 people, U.S. military officials told NBC News.

Two U.S. warships in the Mediterranean Sea fired 59 Tomahawk cruise missiles intended for a single target: Shayrat Airfield in Homs province in western Syria, the Defense Department said. That's the airfield from which the United States believes the government of Syrian President Bashar al-Assad fired the banned weapons.

The Syrian military said the strike killed at least seven people and wounded nine others, according to The Associated Press. Russia's foreign minister said no Russian servicemen were hurt.

It was the first direct American assault on the Syrian government and Trump's most dramatic military order since becoming president just over two months ago. The strikes also risk thrusting the U.S. deeper into an intractable conflict that his predecessor spent years trying to avoid.

Announcing the assault from his Florida resort, Trump said there was no doubt Syrian President Bashar Assad was responsible for the chemical attack, which he said employed banned gases and killed dozens.

"Assad choked out the lives of helpless men, women and children," Trump declared, deeming the strike in the "vital national security interest" of the United States.

He called on "civilized nations" to join U.S. in "seeking to end the slaughter and bloodshed in Syria." Some U.S. allies backed the move, while Russia called it "thoughtless" and promised to help fortify Syria's air defenses.

Talal Barazi, the governor of Homs province, had earlier said a fire raged in the air base in Homs for over an hour following the barrage.

U.S. officials told NBC News that people were not targeted and that aircraft and infrastructure at the site were hit, including the runway and fuel pumps.

"We are assessing the results of the strike. 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 statement said.

Ahrar Al Sham, the largest Syrian rebel group, released a statement backing the U.S. airstrikes.

"The armed opposition welcomes any US intervention through surgical strikes that would deter the Assad regime capabilities to kill civilians and shorten the suffering of our people," the statement said.

The Pentagon said the U.S. took careful precautions to avoid casualties, including the time of day they chose for the strike. Several members of Congress were also briefed on the administration's decision to strike the base, though some lawmakers were concerned by what they viewed as an "act of war" that "raised more questions that answers."

Trump suggested that Assad may have to leave power, and his comments were strongly underscored by Secretary of State Rex Tillerson, who told reporters "there's no role for him to govern the Syrian people."

Tillerson said late Thursday that Russia has "failed to deliver" on preventing chemical weapons attacks in Syria, adding that Russia has either been "complicit or simply incompetent."

Support for the strikes from the U.S. poured in early Friday, including statements from Turkey, Israel, Saudi Arabia, Japan and Australia.

Numan Kurtulmus, deputy prime minister of Turkey, welcomed the strike as an "important and meaningful" development but stressed that a continued tough stance is needed. He added that Assad's regime "must immediately be stopped."

Prime Minister Benjamin Netanyahu wrote on Twitter that Trump "sent a strong and clear message today," hoping it will resonate "not only in Damascus but in Tehran, Pyongyang & elsewhere."

Russia and Iran condemned the U.S. missile strike on Syria. The Kremlin said Russian President Vladmir Putin sees the strike as an "aggression against a sovereign state in violation of international law."

"Washington's move impairs the Russian-US relations, which are in a deplorable state," spokesman Dmitry Peskov said.

The Russian Foreign Ministry later announced it was suspending a deal with the U.S. on protecting Syria's airspace.

Iran called it a "dangerous" and "destructive" act, one that "violates the principles of international law." Officials there also warned it would "strengthen terrorists" and further add to "the complexity of the situation in Syria and the region."

The Trump administration has been put to the test this week amid an international outcry over the newly horrifying violence in Syria. Over the past seven years, hundreds of thousands of people have been killed in the nation's civil war, triggering the worst refugee crisis since World War II.

The strike came as Trump was hosting Chinese President Xi Jinping in meetings focused in part on another pressing U.S. security dilemma: North Korea's nuclear program. Trump's actions in Syria could signal to China that the new president isn't afraid of unilateral military steps, even if key nations like China are standing in the way.

Trump has advocated greater counterterrorism cooperation with Russia, Assad's most powerful military backer. Just last week, the Trump administration signaled the U.S. was no longer interested in trying to push Assad from power.

U.S. military officials sought to portray the strikes as an appropriate, measured response. But the assault still risks plunging America into the middle of Syria's conflict, complicating the safety of the hundreds of U.S. forces fighting a separate campaign against ISIS in the north of the country. If Assad's military persists in further gas attacks, the Trump administration has indicated it would pursue increased retaliation.

Russia and Iran, Assad's allies, pose other problems. Russian military personnel and aircraft are embedded with Syria's, and Iranian troops and paramilitary forces are also on the ground helping Assad fight the array of opposition groups hoping to topple him.

U.S. military officials said they informed their Russian counterparts of the impending attack. The goal was to avoid any accident involving Russian forces.

Nevertheless, Russia's Deputy U.N. ambassador Vladimir Safronkov warned that any negative consequences from the strikes would be on the "shoulders of those who initiated such a doubtful and tragic enterprise."

The U.S. also notified its partner countries in the region prior to launching the strikes.

Trump's decision to attack Syria came three-and-a-half years after President Barack Obama threatened Assad with military action after an earlier chemical weapons attack killed hundreds outside of Damascus. Obama had declared the use of such weapons a "red line." At the time, several American ships in the Mediterranean were poised to launch missiles, only for Obama to abruptly pull back after key U.S. ally Britain and the U.S. Congress balked at his plan.

He opted instead for a Russian-backed plan that was supposed to remove and eliminate Syria's chemical weapons stockpiles.

Thursday night's strikes were launched from the USS Ross and USS Porter and landed in the early morning Friday in Syria.

The world learned of the chemical attack earlier in the week in footage that showed people dying in the streets and bodies of children stacked in piles. The international outcry fueled an emotional response from Trump, who appeared to abandon his much-touted "America First" vision for a stance of humanitarian intervention, akin to that of previous American leaders. "I think what happened in Syria is a disgrace to humanity," he said Thursday.

Trump seemed to rapidly reconsider his feelings about Assad, saying: "He's there and I guess he's running things, so something should happen."

The show of force in Syria raises legal questions. It's unclear what authority Trump is relying on to attack another government. When Obama intervened in Libya in 2011, he used a U.N. Security Council mandate and NATO's overall leadership of the mission to argue that he had legal authority — arguments that many Republicans opposed. Trump can't rely on either justification here.

Unclear also is whether Trump is adopting any broader effort to combat Assad. Under Obama, the United States largely pulled back from its support for so-called "moderate" rebels when Russia's military intervention in September 2015 led them to suffer a series of battlefield defeats. Instead, Obama sought to work with Russia on a negotiated transition.