A U.S.-led coalition airstrike on a gas distribution facility in a stronghold of the Islamic State group set off a series of secondary explosions and killed at least eight people in eastern Syria, activists said Saturday.

The airstrike targeted a distribution station in the town of Khasham in the oil-rich province of Deir el-Zour late Friday, Deir el-Zour Free Radio, an activist collective, said on its Facebook page. The collective named four of those killed and said another four charred bodies were placed in a nearby mosque. It said the slain men were mostly fuel tanker drivers.

Another activist group, the Deir el-Zour Network, described "long tongues of flames" from the strike. The incident was also reported by the Britain-based Syrian Observatory for Human Rights, which relies on a network of activists inside Syria.

The U.S.-led coalition has aggressively targeted IS-held oil facilities in Syria, which provide a key source of income for the militants. But such strikes also endanger civilians, which could undermine long-term efforts to destroy the group.

Other airstrikes late Friday targeted oil wells in the Deir el-Zour province, the activists said.

There was no immediate comment by the U.S. military.

The U.S.-led coalition began a bombing campaign against the IS group in Syria in late September after striking at the extremists in neighboring Iraq, where they also hold swaths of territory.

In recent days, much of the coalition's strikes have focused around the Syrian border town of Kobani, also known as Ayn Arab, which IS militants have been trying to seize since mid-September.

On Saturday, Islamic State militants fired a barrage of mortar rounds toward Kobani, focusing their efforts near the border crossing with Turkey. Some of the shells landed in Turkish territory, but did not cause any damage. As gun and mortar fire in the town echoed across the border, at least five coalition airstrikes sent plumes of black smoke into the sky.

Idriss Nassan, a senior Kobani official, said the airstrikes had helped halt the advance of the militants. But he said the Kurdish fighters defending Kobani would need more weapons and ammunition to save the town.

"Airstrikes are not enough," said Nassan. "It's reduced ISIS, but it's not enough to defeat them," he said.

The Kurdish forces' efforts to rearm have been stymied by Turkey, which has long viewed the main Kurdish fighting force in Kobani -- the People's Protection Units, or YPG -- with suspicion over its links to the Kurdish PKK insurgent group operating in Turkey. Turkey has also demanded that the coalition widen its campaign against the IS group by providing greater aid to Syrian rebels, who are battling both the extremist group and President Bashar Assad's forces.

Syrian government airstrikes on a rebel-held town near Damascus killed at least 16 people late Friday as part of intensified efforts by government forces to secure approaches to the capital, activists said.

At least five strikes targeted the town of Douma on Friday evening, said local activist Hassan Taqulden and the Observatory, which said the bombs killed at least three children and one woman.

"There are people under the rubble and we can't help them," Taqulden said. An online video purportedly showing the aftermath of the strikes showed a bloodied little girl with a bandage around her head and a toddler on a hospital cot. The video appeared genuine and was consistent with Associated Press reporting.

Syrian state media said late Friday that government forces had attacked "terrorists" in Douma. The government routinely refers to rebels as terrorists, and does not acknowledge civilian casualties.

Syria's air force has stepped up its bombing of Douma over the past three months as part of a broader battle to assert government control around Damascus and prevent rebels from staging attacks from the city's outskirts. Rebel attacks have also killed scores of civilians.

Activists say Syria's three-year civil war has killed more than 200,000 people.