An Israeli air strike on a government-held village on the Syrian side of the Golan Heights ceasefire line killed five pro-regime forces on Wednesday, a monitoring group said.

"An Israeli plane hit a car inside the town of Hader, killing two men from (Lebanese Shiite group) Hezbollah, and three men from the pro-regime popular committees in the town," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

Hader is a Druze village that lies along the ceasefire line, with the Israeli-occupied portion of the Golan Heights plateau to the west, and the border with Damascus province to the northeast.

An Israeli army spokeswoman declined to comment on the incident.

According to Hezbollah's official television station Al-Manar, "two members of Syria's (pro-regime militia) National Defence Forces were killed when an Israeli drone targeted their car at the entrance of Hader, in Quneitra province."

Lebanon's Hezbollah is a close ally of the Syrian government and has dispatched fighters to bolster the army against the uprising that began in March 2011.

Israeli air strikes have targeted Hezbollah and regime army positions in Syria in the past.

In January, an Israeli raid near Quneitra killed six Hezbollah fighters, including the son of a senior assassinated commander, and an Iranian general.

Israel has carried out at least five air strikes in the region since early 2014, although it has also been accused of additional strikes elsewhere in Syria and has also returned fire across the ceasefire line.

Rebel fighters, including Islamists, have almost completely surrounded Hader for over a month after fierce clashes with loyalist militia.

Israel's own significant Druze minority has expressed concern that their brethren in Syria would be targeted by rebels there.

The Druze are a secretive offshoot of Shiite Islam. Officials say there are 110,000 of them in northern Israel and another 20,000 in the Israeli-occupied Golan.

Israel seized 1,200 square kilometres (460 square miles) of the Golan Heights from neighbouring Syria in the 1967 Six Day War.