Missiles struck an air base in central Syria early on Monday, the country's state-run news agency reported, killing at least 14 people, including Iranians, according to a war-monitoring group.

The Russian military says the Israeli Air Force was behind the airstrike in Syria and had launched eight missiles on a Syrian air base.

A Syrian military official also says Israel was behind the attack.

Russia's Defense Ministry says two Israeli fighter jets launched the attack on the T4 air base in central Syria from Lebanon's air space in the early hours on Monday.

The ministry says Syria shot down five out of the eight missiles that targeted the base. It says the other three landed in the western part of the T4 base.

Syrian state TV meanwhile quoted the unnamed military official as saying Israeli F-15 warplanes had fired several missiles while flying over neighboring Lebanon. The TV gave no further details.

Previously, the SANA news agency said it was likely "an American aggression," however U.S. officials said the United States had not launched the strikes.

Israel has also struck inside Syria in recent years. The Israeli military had no immediate comment Monday on the reported missile strike.

The missile attack followed a suspected poison gas attack on Saturday on the last remaining foothold for Syrian rebels in the eastern suburbs of Damascus. At least 40 people were killed in that assault, including families found in their homes and shelters, opposition activists and local rescuers said.

Earlier, President Donald Trump had promised a "big price to pay" for the suspected chemical attack. After the airstrikes were reported, however, Pentagon spokesman Christopher Sherwood said in a statement that "at this time, the Department of Defense is not conducting airstrikes in Syria."

The U.S. launched several dozen Tomahawk cruise missiles at a Syrian air base last year, after a chemical attack in the northern Syrian town of Khan Sheikhoun killed dozens of people.

Saturday's suspected poison gas attack on the besieged town of Douma came almost exactly a year after the U.S. missile attack prompted by the Khan Sheikhoun deaths.

In response to the reports, Trump on Sunday blamed Syrian government forces for what he called a "mindless CHEMICAL attack." In a series of tweets, Trump held Russia and Iran, Syrian President Bashar Assad's chief sponsors, responsible.

The Syrian government denied the allegations, calling them fabrications.

First responders entering apartments in Douma late Saturday said they found bodies collapsed on floors, some foaming at the mouth. The opposition's Syrian Civil Defense rescue organization said the victims appeared to have suffocated.

The organization, also known as the White Helmets, and the Syrian American Medical Society, a medical relief organization, did not identify the substance used but said survivors treated at clinics smelled strongly of chlorine.

Those reports could not be independently verified because of a government blockade around the town.

Hours after the attack, the Army of Islam rebel group agreed to surrender the town and evacuate their fighters to rebel-held northern Syria, Syrian state media reported. The group also agreed to give up its prisoners, a key government demand.

The government agreed to halt its assault after three days of indiscriminate air and ground attacks.

"There's nothing left for civilians and fighters. We don't have anything to stand fast," said Haitham Bakkar, an opposition activist inside the town. He spoke to The Associated Press by WhatsApp.

More than 100 buses entered the town Sunday night to transport fighters and their families to Jarablus, a town under the shared control of rebels and Turkey, said Syrian state-affiliated al-Ikhbariya TV.

The preparations follow a pattern of evacuations around the capital, Damascus, and other major Syrian cities as the government reasserts its control after seven years of war.

Human rights groups and U.N. officials say the tactic amounts to forced displacement, a war crime. The U.N. Security Council planned to hold an emergency meeting Monday to discuss the chemical attack.

In his tweets Sunday, Trump called Assad an "animal" and delivered a rare personal criticism of Russian President Vladimir Putin for supporting him. Trump has declared his intent to withdraw U.S. troops from Syria in the coming months, despite resistance from many of his advisers.

Bakkar, the opposition activist, said several bombs laced with chemicals landed in Douma Saturday night. Another activist, Bilal Abou Salah, said a large, yellow cylinder smashed through the roof of an apartment building and came to rest on the third floor and started to discharge gas.

Rescuers from the White Helmets documented 42 fatalities but were impeded from searching further by strong odors that caused breathing difficulties, said Siraj Mahmoud, a spokesman for the group.

A joint statement by the White Helmets and the medical society said more than 500 people, mostly women and children, were brought to medical centers complaining of difficulties breathing, foaming at the mouth and burning sensations in the eyes. Some had bluish skin, a sign of oxygen deprivation.

The symptoms were consistent with chemical exposure. One patient, a woman, had convulsions and pinpoint pupils, suggesting exposure to a nerve agent, the statement said.

The Observatory gave a higher death toll, saying at least 80 people were killed in Douma, including around 40 who died from suffocation. But it said the suffocations were the result of shelters collapsing on people inside them.

The Syrian government, in a statement on SANA, denied the allegations, calling them "fabrications" by the Army of Islam and a "failed attempt" to impede government advances.

"The army, which is advancing rapidly and with determination, does not need to use any kind of chemical agents," the statement said.

Russia denied any involvement in the attack. Maj. Gen. Yuri Yevtushenko was quoted by Russian news agencies Sunday as saying Russia was prepared to send specialists to Douma to "confirm the fabricated nature" of the reports.

Douma has been crippled by close to five years of siege by government forces. It was once one of the hubs of the 2011 Arab Spring uprising against Assad's government.

In recent weeks, government forces have recaptured villages and towns in the eastern Ghouta suburbs of the capital. Douma was the only town left holding out.

A 2013 chemical attack in eastern Ghouta that killed hundreds of people was widely blamed on government forces. The U.S. threatened military action but later backed down.

Syria denies ever using chemical weapons during the war and says it eliminated its chemical arsenal under a 2013 agreement brokered by the U.S. and Russia.

___

Associated Press writer James Heintz in Moscow, Tia Goldenberg in Jerusalem and Jonathan Lemire in Washington contributed to this report.