The Syrian Observatory for Human Rights on Monday said missile strikes had killed at least 26 pro-regime fighters, most of whom were Iranians, AFP reported. Sixty fighters were wounded and several others are missing, it said, adding that the toll could rise.

“At least 26 fighters were killed, including four Syrians,” the monitor said, adding that the main target of the strike was a military base in the province of Hama.

The Syrian Observatory for Human Rights’ head Rami Abdel Rahman said, “Given the nature of the target, it is likely to have been an Israeli strike.” he said. The strikes also reportedly hit an air base in nearby Aleppo province, where surface-to-surface missiles were stored.

Israeli Intelligence Minister Yisrael Katz said on Monday that he was “not aware” of the strikes.

The attack comes during heightened tensions between Iran and Israel following an airstrike on April 9 in the central Syrian province of Homs. Syria and its allies Russia and Iran had blamed Israel for the attack but Jerusalem neither confirmed nor denied it.

Barely a week later, the United States and its allies United Kingdom and France ordered missile strikes against Syria in retaliation for a suspected chemical attack in the rebel-held Douma town by the Bashar al-Assad regime, reportedly killing dozens of people.