Trump warns Russia about shooting down missiles in Syria: 'Get ready'

President Donald Trump appeared to fire a warning shot at Russia on Wednesday morning, saying via Twitter that the country should "get ready" for missiles fired at Syria and that it should not "be partners with a Gas Killing Animal."

He tweeted: "Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and 'smart!' You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!"

On Monday, Trump vowed during a Cabinet meeting at the White House that the United States would make "some major decisions over the next 24 to 48 hours" on how to respond to a suspected chemical attack in Syria over the weekend, which he called "atrocious."

Maria Zakharova, a spokeswoman for Russia's foreign ministry, responded to Trump's tweet Wednesday, saying any missiles launched in retaliation should target terrorists, not the Syrian government.

"Smart rockets ought to fly toward terrorists and not at a lawful government, which has been fighting for several years with international terrorism on its territory," Zakharova wrote in Russian on her Facebook page. "And yes, incidentally. Have they warned the [Organization for the Prohibition of Chemical Weapons] inspectors that now smart rockets will annihilate all evidence of chemical weapons on the ground? Or does the whole idea consist in quickly covering the traces of the provocation with strikes from smart rockets and international inspectors will already have nothing to look for in terms of evidence?"

Vladislav Volodin, the speaker of Russia's lower house of parliament, said the "whole world is horrified by" Trump's tweeting.

"The president is sitting there on Twitter taking such decisions that whole world are horrified by. It is not our way,” Volodin said during an address to parliament in Moscow Wednesday, according to the Interfax news agency.

In a follow-up tweet, Trump said America's relationship with Russia "is worse now than it has ever been." Then he added, "There is no reason for this."

"Our relationship with Russia is worse now than it has ever been, and that includes the Cold War. There is no reason for this. Russia needs us to help with their economy, something that would be very easy to do, and we need all nations to work together. Stop the arms race?" he wrote.

Syria's ongoing conflict started as a local protest movement in the southern city of Dara'a before expanding into a full-fledged civil war by 2012. ISIS, which grew out of Al Qaeda in Iraq, took root in northern and eastern Syria in 2013 after seizing swaths of territory in neighboring Iraq. The jihadist group is fighting to overthrow President Bashar al-Assad's regime and establish a caliphate.

The Syrian Civil War has pulled in the United States, Russia, Iran and almost all of Syria's neighbors. It has sparked the largest humanitarian and refugee crisis since World War II, according to the United Nations.

The World Health Organization condemned the suspected use of toxic chemicals in the rebel-held enclave of Eastern Ghouta in the Syrian city of Douma over the weekend. The WHO said in a statement Wednesday that, according to reports from its partners, "an estimated 500 patients presented to health facilities exhibiting signs and symptoms consistent with exposure to toxic chemicals."

"More than 70 people sheltering in basements have reportedly died, with 43 of those deaths related to symptoms consistent with exposure to highly toxic chemicals," the organization added. "Two health facilities were also reportedly affected by these attacks."

ABC News' Tom Liddy, Patrick Reevell and Morgan Winsor contributed to this report.