Explosions at a Syrian military base housing a weapons warehouse Friday were the result of human error" while moving ammunition, the defense ministry said. Ten civilians outside the base were hurt, a local doctor said.
However, the Britain-based Syrian Observatory for Human Rights, a war monitoring group, said the blasts at the base near the central city of Homs were caused by a suspected Israeli rocket attack.
The group said Syrian air defenses were activated before the explosions, suggesting they were responding to an incoming attack.
The Observatory said the warehouse was used by Lebanon's Iran-backed militant Hezbollah group, which is fighting alongside Syrian government forces in the country's nine-year civil war.
The Israeli military, which declined to comment, has in the past targeted Iranian and Iranian-backed targets in Syria, saying it won't tolerate Tehran's increasing influence along its borders.
There have recently been several reports of suspected Israeli strikes inside Syria, the last on Monday, when the Syrian military and state media said Israeli warplanes flying over Lebanon fired missiles toward areas near the Syrian capital, Damascus, killing three civilians.
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The Observatory said four Iran-backed fighters were also killed.
The divergent accounts for Friday's explosions could not be immediately reconciled.
The Syrian government rarely acknowledges Iran and Iranian-backed groups, which have been instrumental in turning the tide of the war in favour of the government, use its military bases and facilities.
After the blasts, which were heard inside the city, smoke could be seen from a distance. The local health director, Hassan al-Guindi, told state media that 10 civilians were injured as they walked by the site.
The provincial governor, Talal Barazi, said the base houses a weapons warehouse. The Observatory said the explosions damaged the base and sent debris flying outside its perimeters.
Separately, Syrian state media reported late Thursday that Israeli helicopters flew over the occupied Golan Heights firing at unidentified targets and causing material damage.
Israel has acknowledged carrying out scores of airstrikes over the years, most aimed at alleged Iranian weapons shipments believed to be bound for Hezbollah.
Israeli officials have expressed concerns Hezbollah is trying to establish production facilities for precision-guided missiles.
In recent weeks, suspected Israeli attacks included the targeting of Iranian-backed fighters in the desert near the central Syrian town of Palmyra, and an Israeli drone attack on a SUV carrying Hezbollah members close to the border with Lebanon.
In other developments Friday, residents in opposition-held northwest Syria, which is home to 3 million people, rallied against the al-Qaida-linked Hayat Tahrir al-Sham group, a day after its militants shot at demonstrators and killed a protester.
Thursday's demonstration was called to denounce the militants' plan to set up a crossing point between the opposition areas and towns and villages captured by government forces in March.
The crossing was to help the militants' tax collection from the trade of goods between the areas.
Taxation on otherwise smuggled goods are the main source of income for the al-Qaida-linked group.
The shots killed 41-year-old protester Salah Maree, who was buried Friday.
Ezzeddin al-Idlilbi, an activist who was at the protest in the town of Maarat al-Nassan on Thursday, said Maree had already lost three of his children in the war and was a former political prisoner of the Syrian government.
Hayat Tahrir al-Sham, the most powerful militant group in Syria's opposition-held areas, said it was saddened by the death and that it would suspend the opening of the crossing.
Although the group has sought to distance itself from the al-Qaida network, the U.S and Turkey have placed it on their list of terrorist groups.