Islamic State group jihadists have attacked an oil and gas field in Syria, killing at least 30 pro-regime gunmen and security guards, a monitoring group said Wednesday.

"IS managed to control parts of the field," the Syrian Observatory for Human Rights, which relies on a wide network of sources in the war-torn country, said after Tuesday's assault at Shaer, in Homs province.

An unknown number of jihadists were also killed, Observatory director Rami Abdel Rahman told AFP.

An earlier attack by IS fighters on Shaer in July left 270 people dead, including soldiers and pro-regime fighters.

Most were reportedly executed at gunpoint after being taken prisoner.

IS has targeted oil and gas facilities in Iraq and Syria as it seeks funds for its fight to seize territory for a self-proclaimed Islamic "caliphate".