BEIRUT — A strong explosion struck a weapons market in an eastern Syrian town near the border with Iraq Saturday, killing at least eight people and wounding many others, state media and activists said.

Syrian state TV said the blast in the town of Mayadeen killed 30 people and wounded many others, while the Britain-based Syrian Observatory for Human Rights said eight people were killed and 21 wounded, including some who are in critical condition.

Mayadeen is about 37 miles from the Iraqi border in Syria’s eastern oil-rich province of Deir el-Zour, which has seen heavy fighting among rival rebel factions as well as between government forces and opposition fighters.

The blast came days after fighters of the al-Qaida-breakaway Islamic State of Iraq and the Levant launched a wide offensive in northern and central Iraq capturing much of the border between the two countries.

The Islamic State, which is largely composed of foreign jihadists, has made significant headway in eastern Syria over the past six weeks, seizing towns and villages in heavy fighting against the al-Qaida-affiliated Nusra Front and other Islamic rebel groups.

The Observatory said the blast occurred when a bomb exploded accidentally in the car of a local arms dealer who was in the market to sell the device, also setting off ammunition in the area.

To the northwest, state media and the Observatory reported heavy clashes in the coastal province of Latakia, a government stronghold that opposition fighters were able to penetrate in March.

Earlier Saturday, Jordan’s state-run news agency reported that border guards opened fire on four vehicles trying to enter illegally from Syria after they ignored orders to stop. It did not say whether anyone was killed or wounded in the incident.

The Petra news agency said the incident took place Friday. Officials could not immediately be reached to provide further details.

Jordan hosts nearly 600,000 registered Syrian refugees – although Jordanian officials say the real number is far higher.

The kingdom has quietly supported Syria’s rebels since the start of the uprising against President Bashar Assad in 2011, and ordered Syria’s ambassador out last month after accusing him of making “offensive” statements about Jordan.

Syria’s conflict, now in its fourth year, has killed at least 160,000 people, according to activists. Nearly three million Syrians have fled the country.