Ammon News - AMMONNEWS - Syrian state media, citing a military source, said on Monday that Israeli F-15 war planes had conducted the overnight missile attack on a major air base in central Syria.

"The Israeli aggression on the T4 airport was carried out with F-15 planes that fired several missiles from above Lebanese land," state news agency SANA said.

Russian military sources also said that two Israeli F-15 war planes had carried out strikes on a Syrian air base on Sunday.

Interfax cited the Russian Defence Ministry as saying the Israeli war planes had carried out the strikes from Lebanese air space, and that Syrian air defence systems had shot down five of eight missiles fired.

Asked about the Russian statement, an Israeli military spokesman said he had no immediate comment.

Syrian state TV said on Monday the United States was suspected of striking an air base hours after US President Donald Trump warned of a "big price to pay" as aid groups said dozens of people were killed by poison gas in Douma, a rebel-held town.

The US denied it was conducting air strikes in Syria.

"At this time, the Department of Defense is not conducting air strikes in Syria," a Pentagon spokesman said.

"However, we continue to closely watch the situation and support the ongoing diplomatic efforts to hold those who use chemical weapons, in Syria and otherwise, accountable."

Iranians killed
The strike killed 14 fighters, including allied Iranian forces, a monitoring group said on Monday.

"At least 14 fighters were killed in the strike on the T-4 airport, among them Iranian forces," said the Syrian Observatory for Human Rights, a Britain-based war monitor.

Douma chemical attack
That followed a warning by US President Donald Trump on Sunday that there would be a "big price to pay" after medical aid groups reported dozens of people were killed by poison gas in Douma, a besieged rebel-held town in Syria.

"Many dead, including women and children, in mindless CHEMICAL attack in Syria," Trump wrote on Twitter, lashing out at Syrian President Bashar al-Assad and Russia's Vladimir Putin, a key ally of the regime.

"President Putin, Russia and Iran are responsible for backing Animal Assad. Big price to pay," he said.

His comments came exactly a year and a day after the US fired cruise missiles at a Syrian air base in retaliation for a deadly sarin gas attack in 2017.

*Agencies