The head of the Syrian branch of al-Qaeda has denounced US-led air raids in the country, warning of retaliatory attacks in the "homes" of the Western and Arab countries that have taken part in the bombings.

In an audio message posted online on Monday, Abu Mohammad al-Golani, the leader of the Nusra Front, called on European and US citizens to denounce Washington's actions.

"Muslims will not watch while their sons are bombed. Your leaders will not be the only ones who would pay the price of the war. You will pay the heaviest price," he said, warning that the battle would be brought "to the hearts of your homes".

Your leaders will not be the only ones who would pay the price of the war. You will pay the heaviest price.

Abu Mohammad al-Golani, leader of the Nusra Front

Failure to stop these strikes "will transfer the battle to your very homes", Jolani said.

The warning comes a day after the group's spokesman, Abu Firas al-Suri, also threatened reprisals against nations participating in the attacked and denounced them as "a war against Islam".

The US has been carrying out attacks against ISIL fighters in neighbouring Iraq since August 8, and on September 23 began attacking the group's fighters in Syria.

At least 50 fighters from the Nusra Front were killed in the first wave of the US-led attacks in Syria last Tuesday, a British-based monitoring group said.

Washington says the campaign, backed to varying degrees by Arab and Western allies, is aimed at "degrading and destroying" ISIL who have captured large swathes of both Syria and Iraq.

Golani's message comes after the US-led coalition targeted four ISIL positions overnight across four provinces in northern and eastern Syria, hitting a grain silo as well as the country's largest gas plant, activists said.

The UK-based Syrian Observatory for Human Rights said coalition forces hit ISIL facilities in Aleppo, Raqqa, Hassakeh and Deir el-Zor provinces. 

Among the facilities hit was the entrance to Syria's largest gas plant, Conoco in Deir el-Zor, and a grain silo in the ISIL-held town of Manbij in Aleppo province. 

The observatory also said at least 19 civilians had been killed so far in coalition raids. Al Jazeera could not confirm the observatory's figures.

Source: Agencies