Three people were killed when Iranian tanker was attacked off Syria's coast on Saturday, a Syrian war monitor said.
"At least three Syrians were killed, including two members of the crew" in the attack that sparked a fire, said Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights.
"The Iranian tanker came from Iran and was not far from Baniyas port," he said.
It was not clear who carried out the attack or whether a drone or missile was used, he said. "We don't know if this was an Israeli attack," he told AFP.
Quoting the Syrian oil ministry, state news agency SANA said the fire erupted after "what was believed to be an attack by a drone from the direction of Lebanese waters". The flames were later extinguished.
Hundreds of Israeli air strikes have struck Syria since the war began in 2011, mostly targeting Damascus regime allies from Iran and the Lebanese Hezbollah movement, and Syrian government troops.
The Baniyas oil refinery is located in the regime-controlled coastal province of Tartus.
"It's the first such attack on an oil tanker but the Baniyas terminal has been targeted in the past," Mr Abdel Rahman said.
Early last year, Damascus said divers had planted explosives on offshore pipelines of the Baniyas refinery but the damage had not halted operations.
In February 2020, four oil and gas sites in the central province of Homs were attacked by armed drones, sparking fires and causing material damage.
Saturday's attack comes days after a Syrian officer was killed and three soldiers wounded in strikes launched by Israel after a missile was fired towards a secretive nuclear site in southern Israel.
The Israeli army said at the time that a surface-to-air missile had been fired from Syria toward the southern Negev desert, where the Dimona nuclear reactor is located.
Israel is considered the leading military power in the Middle East and is widely believed to possess its sole nuclear arsenal.
Its quantity remains undisclosed but foreign experts estimate it to to be between 100 to 300 nuclear warheads.
Syrian oil the costly prize in Iran-Israel conflict
Israel has long sought to prevent bitter foe Iran from establishing itself in war-torn Syria.
Before the war, Syria enjoyed relative energy autonomy but production has plummeted during the war, pushing the government to rely on imports.
Western sanctions on oil shipping, as well as US punitive measures against Iran, have complicated these imports.
Pre-war production was 400,000 barrels per day (bpd) in Syria.
But it stood at just 89,000 bpd in 2020, Syria's oil minister said in February, of which up to 80,000 came from Kurdish areas outside government control.