The Syrian regime, which denounced a "fresh aggression" after the strikes, meanwhile continued to flush out armed groups from the capital with more deals to transfer fighters to the country's north.

According to the Syrian Observatory for Human Rights monitoring group, missile strikes hit two military targets in Aleppo and Hama provinces late Sunday.

The strike on Hama province hit a base known as the 47th Brigade where pro-regime fighters are stationed. Both hits destroyed surface-to-surface missiles, the monitor said.

"At least 26 fighters were killed, including four Syrians," in the Hama strike, said Rami Abdel Rahman, who heads the Britain-based monitoring organisation.

"The others are foreign fighters, a vast majority of them Iranians," he told AFP. "Given the nature of the target, it is likely to have been an Israeli strike."

Israeli Intelligence Minister Yisrael Katz told army radio on Monday morning that he was "not aware" of the latest strikes.

But, he said, "all the violence and instability in Syria is the result of Iran's attempts to establish a military presence there. Israel will not allow the opening of a northern front in Syria."

Israeli media reported that the security cabinet was due to hold an emergency session later Monday.

The latest strikes came amid heightened tensions in Syria after Damascus and its ally Iran accused Israel on April 9 of conducting deadly strikes against a military base in the centre of the country.

- Israel-Iran tension -

At least 14 soldiers, including seven Iranians, were killed in the strike on a military base in Homs province.

Days later, on April 14, the United States, France and Britain bombarded several Syrian regime military positions in response to a suspected chemical attack on the rebel stronghold of Douma which killed dozens, according to rescue services.

Syria remains technically at war with neighbouring Israel, which is concerned at the growing presence of Iranian forces and those of Tehran's Lebanese ally Hezbollah on Syrian territory.

Israeli Defence Minister Avigdor Lieberman vowed in an interview Thursday to strike at any attempt by Iran to establish a "military foothold" in Syria.

Iran has forces deployed in Syria to support the regime of President Bashar al-Assad, as well as supervising the involvement of several Shiite militia groups it sponsors, some of them from other countries such as Iraq or Afghanistan.

There was no immediate comment from Tehran on the Sunday strikes, but the reformist-linked ILNA news agency quoted a security official who did not deny the strike and said any reports on the military situation in Syria should come from Damascus.

"The Syrians must announce the statistics as they are responsible. We are present in this country at the request of the government of Syria," said Hossein Naghavi Hosseini, spokesman for parliamentary national security and foreign policy commission.

- Damascus transfers -

The Syrian government has focused its efforts in 2018 on securing the capital Damascus, the heart of which was spared the worst of the seven-year-old conflict but was long surrounded by rebel-held pockets.

Backed by massive Russian military support, the regime took full control of the Eastern Ghouta enclave earlier this month.

The sprawling semi-rural area east of Damascus had been home to thousands of armed Islamist and jihadist fighters, who were besieged for years but sporadically fired rockets and mortar rounds on the capital.

Pro-regime forces are now battling jihadists from the Islamic State group and other armed groups in southern neighbourhoods of Damascus.

After days of air strikes and heavy fighting, state media reported late Sunday that those areas would be evacuated under deals similar to those that emptied other enclaves around Damascus in recent weeks.

Buses started arriving Monday near Yarmuk, a neighbourhood once home to a Palestinian refugee camp and the main hub of IS forces in southern Damascus, state media reported.

The transfer deal does not include IS fighters, but other jihadists from a former Al-Qaeda affiliate who control pockets inside Yarmuk, Abdel Rahman said.