The US-led coalition against jihadists in Syria struck the entrance to the country's main gas plant late today.

The attack was an apparent warning to so called Islamic State militants to abandon the premises under their control, a monitor said.

"The international coalition has for the first time struck the entrance and prayer area of the Coneco gas plant. It is under IS control, and is the largest in Syria," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

The United States and a group of mainly Gulf Arab allies launched strikes against jihadist positions in Syria on Tuesday.

It came a month and a half after strikes against IS jihadists began in neighbouring Iraq.

Up until today, the strikes had targeted mainly jihadist bases and makeshift oil refineries used by the militants, in a bid to weaken one of their main sources of financing.

The strike against the Coneco gas plant's entrance and prayer area "did not kill any jihadists, though it did injure some of them", Abdel Rahman told AFP.

"It appears as though the international coalition is trying to force the jihadists to leave the plant," he said.

The Coneco gas plant is located in eastern Syria's Deir Ezzor province, which is the country's richest in oil and is located on the Iraq border.

The strike could have significant consequences not only for the jihadists, but also for areas under President Bashar al-Assad's control.

"The Coneco gas plant feeds the Jandar power station located in (regime-held) Homs province," said Abdel Rahman.

"If the Coneco plant stops functioning completely, several regime-held areas, as well as IS-controlled Deir Ezzor province will be left without electricity," he warned.

Before the IS militants took over Deir Ezzor province earlier this year, jihadists from the rival Al-Nusra Front and local tribes had an agreement with Mr Assad's regime to keep the Coneco gas plant up and running.

In exchange for gas, the regime allowed electricity for Deir Ezzor province.

"That agreement was maintained when the IS took over," said Abdel Rahman.