Massive explosions rocked the Hama military air base in western Syrian early on Friday afternoon, killing at least 11 pro-Assad regime fighters, according to the UK-based Syrian Observatory for Human Rights.

Syrian state media confirmed that blasts were heard coming from the base, but made no comment on casualties or the cause of the explosions.

There were conflicting reports as to what set off the blasts, which sent a huge plume of grey smoke into the air above the base.

Get The Times of Israel's Daily Edition by email and never miss our top stories Free Sign Up

“The explosions struck several regime depots of weapons and fuel at Hama military airport,” the Observatory said.

Syrians in Hama reported hearing at least five successive blasts, likely indicating that fuel depots and weapons caches had been hit by the blast, setting off a daisy-chain of explosions.

At least 11 members of Syrian dictator Bashar Assad’s coaltion were killed and dozens more were wounded in the mysterious blasts, according to the monitor.

According to the Observatory, both Syrians and foreign nationals were among the casualties.

The Sky News Arabia outlet reported that the explosions were caused by an attack on an advanced Iranian air defense system.

However, Syrian military sources told the Lebanese el-Nashra TV station that the blasts were caused by a “technical malfunction” at a weapons storage depot.

There were no immediate comments by Syrian officials on who or what was behind the explosions.

The blasts came soon after midday, as the region is experiencing a scorching heat wave. Almost all previous Israeli airstrikes on targets in Syria have been late at night or in the pre-dawn hours.

According to Sky News, the target of the strike was an Iranian Bavar 373 long-range missile defense system, a state-of-the-art model that was unveiled in 2016 and put into service in March 2017. Iranian officials compare the system to the Russian-made S-300 system, which is considered a powerful air defense platform.

Video footage from the scene, posted to social media, showed a huge cloud of smoke rising out of the military air field.

On the night of April 29, the Israeli Air Force carried out missile strikes against a nearby military base, just south of Hama, and another facility in Aleppo, in northern Syria, which Israel believes were used by Iranian forces.

Those air raids were said to have destroyed some 200 missiles and killed at least 26 fighters, mostly Iranians.

[mappress mapid=”6361″]

After maintaining an official policy of refusing to comment on such strikes, the Israeli military last week revealed that it had been conducting air raids against Iranian targets in Syria as part of a mission dubbed “Operation Chess.”

The purpose of “Operation Chess” was to prevent Iran from carrying out reprisals for an Israeli airstrike against the Iranian-controlled T-4 air base in central Syria on April 9, which killed at least seven members of the Islamic Revolutionary Guard Corps, including a senior officer responsible for its drone program.

Iran had also used the T-4 base to launch an attack drone carrying explosives into Israel in February, according to the Israel Defense Forces; the drone was shot down.

The IRGC’s al-Quds Force in southern Syria launched 20 rockets at northern Israel last week. Four of the rockets were intercepted by Israeli air defenses, the army said, and the rest fell short of the border.

In response, the Israeli Air Force conducted strikes against over 50 Iranian military targets in Syria and destroyed several Syrian air defense systems that had fired on Israeli jets, the army said.

Israeli officials have repeatedly stated that the Jewish state will not accept Iranian entrenchment in Syria and is prepared to take military action in order to prevent it.

Last week, the Israeli army reportedly told senior ministers that it believes the current round of hostilities was over, but tensions in the north will persist, and that border incidents are still possible.

The AFP contributed to this report.