There is every reason to believe that Israel was behind Monday's airstrike on a Syrian military base, and not the United States, as Syria at first claimed.

Syria's state-run news agency SANA reported an early morning missile attack on the Tiyas (T-4) air base at Homs, about 100 kilometres north-east of Damascus.

It immediately blamed "likely" US aggression — understandable given the US condemnation of a suspected chemical attack days before on a rebel enclave at Douma outside Damascus.

US President Donald Trump had even warned of a "big price to pay" for the chemical attack, which killed at least 49 people.

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Officials in Washington were working to verify claims by non-government organisations and Syrian opposition activists that the Assad regime was behind the poison attack.

However, the Pentagon denied responsibility for attacking the T-4 base, despite striking similarities to another air strike a year ago, when the US targeted Syria's Shayrat military base — also in Homs province — after another chemical attack in Idlib.

About 90 people died from sarin gas poisoning in that incident, and similar images of dead or dying children circulated online — just as graphic pictures have been broadcast around the world following the Douma attack.

A medical worker giving toddlers oxygen after an alleged poison gas attack in Douma. ( Syrian Civil Defense White Helmets via AP )

Denying the US was behind the T-4 airstrike, the Pentagon said the US supported diplomatic efforts to hold those who use chemical weapons accountable.

Hours later Russia and Syria both said Israeli warplanes had launched the attack. An Israeli spokesperson offered no comment.

And indeed all the evidence for the airstrike points to Israel, which launched a similar bombing raid at Tiyas earlier this year.

In February Israel accused the Syrian regime of allowing Iran to operate the Tiyas base to supply advanced weaponry to Shiite militia groups in the region, including the Lebanese-based Hezbollah, which has long waged war against Israel.

The US is condemning a suspected chemical attack on a rebel enclave at Douma. ( AP: Syrian Civil Defence White Helmets )

It was from this same airbase that Israel says Iran launched a military drone that flew into Israeli airspace in mid-February.

Israeli warplanes shot the drone down and launched raids against Iranian drone installations at Tiyas.

But an Israeli F-16 fighter plane was in turn shot down by Syrian forces.

'More strikes in Syria may be in store'

One intelligence group, Stratfor, says the global condemnation of Saturday's chemical attack gave Israel a window to carry out the airstrike at Tiyas.

"Israel has a narrow window of opportunity to target Hezbollah and other strategic targets while the group is still exposed in the Syrian civil war and while Israel has strong backing from a White House that is particularly hawkish on Iran," it says.

"And with the United States and France vowing a strong joint response to the chemical attack, more strikes in Syria may be in store."

The February drone strike was the first time Israel attacked a manned Iranian base in Syria, although it has struck Syrian army locations many times since the civil war began in 2011, as well as bases and convoys of Iranian-backed militias that fight alongside Syrian forces.

Lebanese media reported the missiles that struck the Tiyas base travelled from the Mediterranean Sea and through Lebanese air space, which would be consistent with an Israeli attack.

Recently too Israel complained that Syria violated a 1974 agreement not to deploy tanks or artillery in a buffer zone that straddles the Israel-Syria border.

The Times of Israel reported last week that the Syrian regime was "preparing an offensive to retake southern Syria and the Syrian Golan Heights from rebel groups, and has reportedly placed tanks and heavy artillery inside the demilitarised buffer zone".

Israel obviously sees any military build-up or chemical attack as a possible threat to its own security and is expected to take its complaint to the United Nations in New York.

US is considering its own response in Syria

Whether or not Israel was behind the Tiyas airbase attack, the US is considering its own response in Syria.

Only last week Mr Trump said he wanted to bring home the 2,000 US troops still on the ground in Syria after the fight against Islamic State militants.

But a senior White House official would not rule out another US missile attack, similar to the one a year ago.

"I wouldn't take anything off the table," homeland security and counterterrorism adviser Thomas Bossert said.

"These are horrible photos [from the chemical attack]. We're looking into the attack at this point."

Other Republicans too are urging the US President to send a powerful message to Syria, Iran and Russia.

"You need to follow with that tweet, show resolve that [former president Barack] Obama never did to get this right," Republican senator Lindsey Graham said.

The global chemical weapons watchdog, Organisation for the Prohibition of Chemical Weapons, said it was gathering all available information about the attack.

The UN Security Council is meeting tomorrow to discuss the latest chemical attack.

ABC/Reuters

