BEIRUT, Lebanon — An Iranian tanker that Western nations sought to bar from delivering its oil has docked and unloaded its cargo on the Mediterranean coast, a spokesman for the Iranian Foreign Ministry said.

Recent satellite images showed the tanker, the Adrian Darya 1, near the Syrian port of Tartus, suggesting that Iran had delivered the oil to the government of President Bashar al-Assad in defiance of European sanctions. But it remained unclear on Monday if the oil went to Syria.

The delivery comes as Western nations have imposed sanctions to punish Mr. al-Assad, an Iranian ally, for alleged war crimes during his country’s civil war. The Trump administration is also pursuing a campaign of “maximum pressure” against Iran aimed at squeezing what it considers Tehran’s destabilizing activities across the Middle East.

Those struggles have played out in recent months on the high seas, with a string of episodes in which Iran and Western nations have seized each other’s tankers, raising tensions all around.