Earlier, state television said successive blasts were heard in rural Hama province and that authorities were investigating the cause.
Will it make one iota of difference if the carriers of death above were Syrian or Russian or Iranian or British or French or American or Israeli?
Analysts on Hadashot News said they did not expect a Syrian or Iranian response to the attack, especially as Iran itself denied any losses in the attack.
A strike carried out on a Syrian base near Hama on Sunday night hit a storage facility and destroyed 200 missiles, according to an official "from a regional alliance that includes Iran, Syria and Hezbollah", quoted by the New York Times.
Lebanon's Al-Akhbar daily, considered close to the militant Iranian-backed Hezbollah group and the Syrian government, said the attack targeted "important arms depots used by the [Syrian] army and Iran's Revolutionary Guards".
Later reports by some media outlets suggested that the missile attack had targeted what they called Iranian military bases and that Iranians were killed as a result.
There was no claim of responsibility for the strikes, but suspicion immediately fell on Israel, which has accused Iran of using the cover of Syria's war to build a military infrastructure there to confront Israel and has vowed to prevent it from developing. Over 18 people were killed and another 60 were wounded, Sky News Arabia reported citing regime media.
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"These are mixed bases for Iran and regime forces inside Syria, Iranian forces are spread out throughout the country".
The strike on Hama province hit a base known as the 47th Brigade where pro-regime fighters are stationed.
However, Iran's Tasnim news agency said reports of Iran's base in Syria being hit by rockets were baseless and no Iranians had been killed.
Activists said the Israelis were behind the offensive which is the third foreign attack on Syria this month, as Israel targeted the T-4 base in the central province of Homs earlier in April and the United States, as well as other Western powers, launched a series of missile strikes on Syrian on April 14. They prefer to refrain from statements which may force them to retaliatory action against Israel - and the lack of such actions will be perceived as empty threats - given the fact that Iran has not managed to answer a previous attack against the base of T4.
Cabinet ministers were also reportedly expected to be presented with a new "development" regarding the Iran nuclear deal, the fate of which it set to be decided by US President Donald Trump in less than two weeks.
Israeli Minister of Military Affairs Avigdor Lieberman said his country will keep operating freely in Syria. The attacks, according to Syria's official SANA media, took place at 10.30 pm.