The US has vowed to keep up the pressure on Syria, despite the prospect of escalating Russian ill-will which could further inflame one of the world's most vexing conflicts.

The Trump administration signalled new sanctions would soon follow Thursday night's cruise missile attack on the government-controlled Shayrat air base in central Syria, where US officials believe Syrian military planes involved in a chemical attack had taken off from.

The Pentagon is also probing whether Russia itself was involved in the chemical weapons assault which compelled Donald Trump to action.

The attack against a Syrian air base was the first US assault against the government of Bashar Assad.

Much of the international community rallied behind Mr Trump's decision to fire the cruise missiles in reaction to the chemical weapons attack which killed dozens of men, women and children in Syria.

A spokesman for Russian president Vladimir Putin warned that the strikes dealt "a significant blow" to relations between Moscow and Washington.

At the United Nations, Russia's deputy ambassador, Vladimir Safronkov, strongly criticised what he called the US "flagrant violation of international law and an act of aggression" whose "consequences for regional and international security could be extremely serious".

He called the Assad government a main force against terrorism and said it deserved the presumption of innocence in the chemical weapons attack.

US officials blame Moscow for propping up Mr Assad.

"The world is waiting for the Russian government to act responsibly in Syria," Nikki Haley, the US ambassador to the UN, said during an emergency Security Council session.

"The world is waiting for Russia to reconsider its misplaced alliance with Bashar Assad."

Thursday night's strikes - involving some 60 cruise missiles fired from two ships in the Mediterranean - were the culmination of a rapid, three-day transformation for Mr Trump, who has long opposed deeper US involvement in Syria's civil war.

Advisers said the US leader was outraged by images of young children who were among the dozens killed in the chemical attack.

The decision undercut another campaign promise for Trump: his pledge to try to warm relations with Moscow.

After months of allegations of ties between his election campaign and the Kremlin - the subject of current congressional and FBI investigations - Mr Trump has found himself clashing with his Russian counterpart.

White House officials cautioned that Mr Trump is not preparing to plunge the US deeper into Syria.

Spokesman Sean Spicer said the missile attack sent a clear message to Mr Assad, but he avoided explicitly calling for the Syrian to leave office.

Mr Trump spent Friday in Florida, in private meetings with Chinese president Xi Jinping.

US officials noted that the timing of the strike had the possible added benefit of signalling to China that Mr Trump is willing to make good on his threat to act alone to stop North Korea's nuclear pursuits if Beijing does not exert more pressure on Pyongyang.

Meanwhile, an air strike by the US-led coalition on a village in northern Syria held by Islamic State (IS) has killed at least 13 civilians, including children, activists said.

Syrian state TV said the strike had killed 13 people, while the UK-based Syrian Observatory for Human Rights said 15 people died in the assault on the village of Hneida.

The village is in the northern province of Raqqa where US-backed Syrian fighters have been on the offensive against IS under the cover of US-led coalition air strikes.

The Sound and Picture activist group, which tracks atrocities by IS, said the air strike hit an internet cafe.

The attack comes at a time of increasing reports of civilian deaths during air strikes by the US-led coalition in northern Syria.

Syrian activists opposed to Islamic State said aircraft from the US-led coalition have struck a boat carrying people fleeing fighting, killing at least seven civilians.

Raqqa is Being Slaughtered Silently said a boat carrying about 40 people was hit as it was crossing the Euphrates River in the northern province of Raqqa.

It said the bodies of a woman and her six children were recovered.

The Sound and Picture group that traces atrocities in areas held by IS also reported the same casualty estimates.

The attack reportedly occurred in the Shuaib al-Zeker area near where US-backed Syrian fighters have been on the offensive against IS under the cover of coalition air strikes.