Here is the latest:

U.S. opted to strike now over concerns Syria was trying to clean up chemical use evidence

Trump indicates more airstrikes possible

Putin complains of 'mendacious' accusations against Assad

UN Security Council rejects Russia's resolution condemning 'aggression' against Syria

Pentagon says 3 chemical weapons sites hit

After striking three sites deemed to be helping the Syrian regime produce chemical weapons, the United States said it won't allow President Bashar al-Assad to continue with any chemical attacks in a civil war that began nearly eight years ago.

"I spoke to the president [Donald Trump] this morning and he said if the Syrian regime uses this poisonous gas again, the United States is locked and loaded," the U.S. ambassador to the United Nations, Nikki Haley, told the UN Security Council on Saturday following the U.S.-led missile strikes.

The U.S. Department of Defence released video of the guided missile destroyer USS Monterey conducting strike operations into Syria while in the Mediterranean Sea 0:33

Trump said the operation, launched around 4 a.m. in Syria and also involving U.S. allies France and Britain, was in response to the "evil and despicable" attack, apparently involving chemical weapons, last weekend on civilians in Douma, near the capital of Damascus. It's estimated the suspected chemical attack, blamed on Assad government, killed at least 40 people, according to non-governmental and aid organizations, although Syria and its ally, Russia, have denied any such weapons were used.

The U.S., Britain and France opted to strike Syria, using an estimated 105 missiles, for its apparent use of chemical weapons without waiting for a report from UN inspectors. U.S. officials said Saturday they were convinced that the Assad government had used chlorine and sarin nerve gas in Douma, and Syrian forces may have already tried to clean up important evidence of chemical weapons use.

On Twitter, Trump praised the military operation as "perfectly executed" and added "Mission Accomplished."

A perfectly executed strike last night. Thank you to France and the United Kingdom for their wisdom and the power of their fine Military. Could not have had a better result. Mission Accomplished! —@realDonaldTrump

The three countries launched their missiles as the fact-finding team from the Organisation for the Prohibition of Chemical Weapons was in the Syrian capital and had been expected to head on Saturday to Douma.

Damage of the Syrian Scientific Research Centre in Barzeh, near Damascus, that was attacked by U.S., British and French military strikes to punish President Bashar al-Assad for suspected chemical attack against civilians in Syria. (SANA/Associated Press ) In Lima, where the Summit of the Americas is being held, U.S. Vice-President Mike Pence said "President Trump made it clear that the United States will not tolerate the use of chemical weapons against men, women and children."

"Last night, U.S. forces brought an extraordinary military effort against chemical weapons facilities, and degraded and crippled the chemical weapons capability of Syria," Pence said. He said the U.S. remains "hopeful" that with the co-operation of the U.K. and France, and support of allies like Canada, "that we will see Syria, and their patrons in Russia and Iran, once and for all abandon the use of chemical weapons against innocent civilians."

Pence met with Trudeau on the sidelines of the summit. Trudeau said Canada supports the decision by the U.S., U.K. and France to bomb targets in Syria, although Canada isn't directly involved in the airstrikes.

Assad's ally, Russia, requested a special session of the UN Security Council after the U.S., France and Britain fired missiles in Syria in the pre-dawn attack Saturday.

The allies struck what they identified as:

A scientific research centre in Barzeh, near Damascus.

A chemical weapons storage facility west of Homs.

A chemical weapons equipment storage facility near Homs.

Airstrikes were carried out beginning around 9 p.m. ET Friday (4 a.m. Saturday Syria time) targeting sites that included a military facility near Homs where it was assessed that Syria had stockpiled chemical weapons, Britain's Ministry of Defence said. (Hassan Ammar/Associated Press)

But the Security Council rejected the Russian resolution calling for condemnation of the "aggression" against Syria by the U.S. and its allies.

Only Russia, China and Bolivia voted in favour of the resolution at the end of an emergency meeting of the 15-member council. Eight countries voted against and three abstained. A resolution needs at least nine favourable votes to be approved.

Haley said the allies have a "large body of evidence" showing Syria used chemical weapons, including sarin, last Saturday.

However, Vasily Nebenzya, the Russian ambassador to the UN, denied there was any evidence of chemical weapons use, and read a statement from Russian President Vladimir Putin that said the U.S. is guilty of delivering a verdict and punishment based on "mendacious" accusations.

"This is hooliganism in international relations," he quoted Putin as saying.

The director of the Joint Staff at the Pentagon, Kenneth McKenzie, said Syria's chemical weapons program has been "set back for years." He described the U.S.-led strikes as "precise, overwhelming and effective."

"As of right now, we are not aware of any civilian casualties," he said and speculated that the 40 surface-to-air missiles the Syrian regime launched during the operation may have hit civilian areas.

The operation was "carefully orchestrated and methodically planned to minimize potential collateral damage, Pentagon spokesperson Dana White said.

"We do not seek conflict in Syria, but we cannot allow such grievous violations of international law," she said.

Syrian television footage shows the aftermath of U.S.-led airstrikes in Syria near Damascus and in Homs. 2:35

The U.S., U.K. and France were expected to brief NATO envoys later Saturday about the airstrikes.

NATO was not involved in the operation, but NATO Secretary General Jens Stoltenberg said Saturday in a statement that he supported the strikes.

"This will reduce the regime's ability to further attack the people of Syria with chemical weapons." ​

U.S. Defence Secretary Jim Mattis and marine Gen. Joseph Dunford said the three main chemical weapons facilities were targeted by missiles from both the sea and aircraft, which triggered Syrian air defences.

Syrian state TV has broadcast images of the destruction at the research centre that was targeted.

The images shown on Al-Ikhbariya TV are the first of the targets. Seen in the footage are piles of rubble outside a destroyed building and a burned vehicle.

France's foreign minister also threatened further missile strikes against Syria in the event of any future chemical weapons use.

British Prime Minister Theresa May said the "despicable and barbaric" attack in Douma killed up to 75 people, including young children, and left as many as 500 other casualties.

Pentagon chief spokesperson Dana W. White and Marine Lt. Gen. Kenneth F. McKenzie Jr. brief the press on operations in Syria 9:53

"For the U.K.'s part, four RAF Tornado GR 4's launched storm shadow missiles at a military facility some 24 kilometres west of Homs, where the regime is assessed to keep chemical weapons in breach of Syria's obligations under the Chemical Weapons Convention," she said.

French Foreign Minister Jean-Yves Le Drian said the attack destroyed a "good part" of the Syrian government's chemical weapons arsenal.

However, although officials said the singular target was Assad's chemical weapons capability, his air force, including helicopters he allegedly has used to drop chemical weapons on civilians, were spared. In a U.S. military action a year ago in response to a sarin gas attack, the Pentagon said missiles took out nearly 20 per cent of the Syrian air force.

'Pretty low' risk of chemicals spreading

Following strikes, there were no immediate reports of casualties, and one expert said the risk of them causing chemicals to spread, which would lead to collateral damage in nearby populations, is "pretty low."

Charles Duelfer, former special adviser to the U.S. director of central intelligence for Iraqi weapons of mass destruction, said the components of chemical weapon production are separated, and that the strikes largely targeted equipment.

A U.S. Air Force B-1B Lancer, deployed to Al Udeid Air Base, is seen in this image from Al Udeid Air Base, Doha, Qatar, that was released on Saturday. (U.S. Air Force handout via Reuters)

"It was mostly production equipment and research equipment they were going after — equipment that will be very hard for the Syrians to replace under sanctions," Duelfer told CBC News.

"There is some risk that toxic chemicals will be spread around," he added. "[But] it's not the risk that it was, say, in 2013 when president [Barack] Obama was considering a much broader strike on the entire infrastructure."

The then president had proposed targeted airstrikes in Syria following reports of chemicals weapons used by the regime.

He sought congressional approval for the action, but the bill never made it to the House or Senate for a vote.

As of Saturday, neither Syria nor its Russian or Iranian allies retaliated, Pentagon officials said.

Iraq and Iran also joined Russia in condemning the airstrikes.

The airstrikes are a "dangerous development," which could be be exploited by "terrorists," Iraq's Foreign Ministry said. Iranian President Hassan Rouhani told Assad in a phone call that Iran "stands by Syria," the Syrian presidency said Saturday.

Germany's chancellor said the allied strikes in Syria were a "necessary and appropriate" response. Angela Merkel said her government believes the U.S., Britain and France "took responsibility in this way as permanent members of the UN Security Council."

The U.S.-led attack will negatively affect peace negotiations, a spokesperson for Russia's Foreign Ministry said, the state-run RIA news agency reported.

Putin called the overnight operation an "act of aggression" that will only worsen the humanitarian crisis in Syria.

Support from Canada

Trudeau issued a statement condemning the apparent attack on Douma in the "strongest possible terms."

He said Canada supports the decision by the U.S., U.K. and France to "take action to degrade the Assad regime's ability to launch chemical weapons attacks against its own people."

"We will continue to work with our international partners to further investigate the use of chemical weapons in Syria. Those responsible must be brought to justice."

Demonstrations held after airstrikes

Following the joint strikes, Syrian state TV carried live images of people dancing and chanting, waving Syrian flags alongside those of Iran and Russia, in support of their government's "steadfastness." Hundreds demonstrated in Umayyad Square in the capital of the Damascus, waving victory signs and honking their car horns in a show of defiance.

One state TV report also said Syrian air defences intercepted most of the incoming missiles, and urged citizens not to believe other media reports "intentionally or unintentionally" exaggerating the results of the attack.

Other rallies were held in Athens, where more than 4,000 people reportedly took part in a rally outside the U.S. Embassy in Greece, and in Washington to protest U.S. intervention in the Syrian conflict.

Protesters with the Answer Coalition gather in front of the White House on Pennsylvania Avenue in Washington on Saturday to denounce the missile strikes in Syria. (Carolyn Kaster/Associated Press)

In other developments Saturday, the Syrian military said it was in control of the eastern Ghouta suburbs of Damascus.

Brig.-Gen. Ali Mayhoub, a spokesperson for the Syrian Armed Forces, read the statement on Syrian TV.

"After a series of concentrated and strong operations for a week, units of our armed forces and allied groups have completed the liberation of eastern Ghouta," Mayhoub said.

Earlier in the day, Syrian police units entered Douma, the last rebel town in the eastern Ghouta region, marking a major victory for Assad.

Douma and the sprawling eastern Ghouta region near Damascus had been under rebel control since 2012 and was a thorn in the side of Assad's government for years.

The entry of government forces to Douma follows a Russian-mediated deal that secured the surrender and evacuation of the rebels and thousands of civilians from the town.