BEIRUT (AP) -- An explosion at a military depot outside Syria's coastal city of Latakia left six people lightly injured on Wednesday, state television said.

State TV said a "technical error" caused the explosion at a base used by the army corps of engineers. The Britain-based Syrian Observatory for Human Rights, which relies on a number of activists on the ground, said it did not know the cause of the explosion in what it described as an ammunition warehouse. It said 13 people were injured, including some in critical condition.

The difference in the casualty figures could not be immediately reconciled. The Observatory said smoke was rising from the depot, on the southern edge of the city. Latakia activists on Facebook also reported the arrival of ambulances and helicopters after the explosion.

Syria's northwestern Latakia province, which borders Turkey, is a regime stronghold whose population belongs predominantly to President Bashar Assad's Alawite sect. The coastal capital Latakia is fully under regime control but some northern parts of the province are in rebel hands.

In villages to the north of the city, government troops on Tuesday destroyed an ammunition dump and several tunnels operated by al-Qaida affiliate Jabhat al-Nusra, Syria's state news agency said on Wednesday. It quoted a military source as saying five Libyan fighters were killed in the operation.

Assad's army has been on an offensive to dislodge rebel fighters from areas they hold in Damascus, as well as the country's heartland in Homs province. That would enable his regime to secure a corridor leading to the coastal enclave that includes Latakia, home to one of the country's two main seaports.

The Syrian uprising began more than two years ago with peaceful protests against Assad, but later grew into a civil war that the U.N. says has killed more than 93,000 people.

The United States decided last week to send arms to the rebel forces. But the G-8 summit of world leaders ended Tuesday without mentioning arms in its final statement, reflecting a split on the issue. The group includes Russia, which opposes the idea.