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 Shia 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."
The National Defence Forces has fighters operating throughout Syria.
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.
Rebel fighters, including Islamists, surrounded the village of Hader on June 17 after fierce clashes with loyalist militia in the area.
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 Shia Islam. Officials say there are 110,000 of them in northern Israel and another 20,000 in the Israeli-occupied Golan.
Israel occupied 1,200 square kilometres (460 square miles) of the Golan Heights from neighbouring Syria in the 1967 Six Day War.