The United Nations, world leaders and human rights groups are pushing for sanctions and a new global outlook on Syria in the wake of its suspected deadly chemical attack that the White House describes as a wake-up call to "the civilized world."

Scores of civilians and children died Tuesday after plumes of either chlorine or the nerve agent sarin shrouded sections of a modest village in northern Syria, the largest suspected use of chemical weapons since 2013. Human rights reports said the gas appeared to be a virulent deadly strain and covered a wider area than past attacks, with many victims collapsing outdoors.

The United Nations Security Council called an emergency session for Wednesday to discuss the attack.

Nikki Haley, U.S. ambassador to the United Nations, said that "more than 60 people, including young children - vomited and gasped for air before they were choked to death - likely at the hands of the Syrian regime."

White House spokesman Sean Spicer said the assault, which burned hundreds of others, "cannot be ignored by the civilized world." He steered blame at the Obama administration in part for "weakness and irresolution" toward Syria. The Trump administration is assessing what action it would take.

“President Obama said in 2012 that he would establish ‘a red line’ against the use of chemical weapons and then did nothing,” Spicer said. "The United States stands with our allies across the globe to condemn this intolerable attack."

The Syrian Observatory for Human Rights, a U.K.-based monitoring group, said 58 people died in the town of Khan Sheikhoun in northern Idlib province, including 11 children. The death toll is likely to rise, the group said.

Turkey said it dispatched 30 ambulances to Idlib following chlorine gas attacks in the northwestern province, the Turkish Anadolu news agency reported. Syrian opposition health minister Firas Jundi put the death toll at more than 100 civilians and said 500 others, mostly children, were sickened or burned by the gas.

"I believe this horrible memory will stay with me for the rest of my life," Jundi told CNN.

If it is confirmed as a chemical attack, it would be the largest in Syria since August 2013, when sarin gas killed hundreds of civilians in Ghouta near Damascus. Reuters reported that the U.S. government believes Sarin may have also been used in the attack Tuesday.

The Syrian anti-government activist group Idlib Media Center published photos of young children receiving medical treatment, and a video showed what appeared to be bodies of children lined up on a blanket. The Syrian government of President Bashar Assad denied using chemical weapons, but the U.S. and international communities were unconvinced. Reuters quoted a U.S. intelligence official who said the poisonous assault "has fingerprints of attack by (the) Assad regime."

"Another vicious chemical attack in #Syria - how do the Syrian people determine their own future while they are being slaughtered?" tweeted Sen. John McCain, chairman of Senate Armed Services Committee.

Secretary of State Rex Tillerson had said last week that ousting Syrian President Bashar Assad's future "will be decided by the Syrian people." The Trump administration has consistently stressed its priority of defeating the Islamic State, rather than deposing Assad.

"There are reports of dozens dead, including many children. While we continue to monitor the terrible situation, it is clear that this is how Bashar al-Assad operates: with brutal, unabashed barbarism," the statement said. "Those who defend and support him, including Russia and Iran, should have no illusions about Assad or his intentions. Anyone who uses chemical weapons to attack his own people shows a fundamental disregard for human decency and must be held accountable."

The statement also called on the countries to act. "As the self-proclaimed guarantors to the cease-fire negotiated in Astana, Russia and Iran also bear great moral responsibility for these deaths."

The New York Times quoted an unnamed State Department official, who said that it appeared Russia was unable or unwilling to hold the Syrian government to the terms of a cease-fire agreement. The official said the attack on civilians appears to be a war crime.

French Foreign Minister Jean-Marc Ayrault called the attack "further evidence of the barbarity suffered by the Syrian people." British Foreign Minister Boris Johnson said he was "horrified" by the attack that "bears all the hallmarks" of chemical weapons previously used by the Syrian regime. Turkish President Recep Tayyip Erdogan called the attack "inhuman" and "unacceptable."

International human rights organization Amnesty International said the reports were alarming and called for an international investigation. Ahmet Üzümcü, who leads the Organization for the Prohibition of Chemical Weapons, said his group was gathering and analyzing information.

Syrian forces loyal to Assad have been involved with chemical weapons before in the brutal, six-year civil war against U.S-backed rebels. Üzümcü's agency implemented a 2013 agreement reached by the U.S. and Russia in 2013 to destroy Syria's chemical weapons arsenal. Still, last year the United Nations issued a report accusing Syria of using internationally banned toxic chemical weapons on civilians in 2014 and 2015.

The toll of war on the battered nation has been enormous. Representatives from more than 50 nations are gathering Wednesday in Brussels for a conference to discuss the financial and humanitarian needs of Syria. The U.N. estimates that 13.5 million people need humanitarian assistance, including 4.7 million people living in besieged or barely accessible areas.