AMMAN/JERUSALEM (Reuters) - Israeli said its forces killed at least five Palestinian militants in an air strike on the Syrian Golan Heights on Friday after cross-border rocket fire from there prompted the heaviest Israeli bombardment since Syria's civil war began in 2011.
An Israeli defense official said the people killed were Palestinian militants from the Iranian-backed Islamic Jihad. "We now know of five or six Palestinian Islamic Jihad terrorists killed," the official said.
A Syrian army source said the 10.30 a.m. (0730 GMT) air strike hit a car in a village in the Syrian Golan, killing five civilians. State television quoted the source as saying it took place near Quneitra, close to the Israeli-occupied side of the Golan.
A Britain-based monitor, the Syrian Observatory for Human Rights, said it counted seven people killed in Israeli air strikes on Thursday and Friday, all of them Syrian soldiers or government-allied militiamen.
There were heavy overnight strikes by Israel against Syrian army posts in the border zone in retaliation for what Israel said were rockets launched from Syria by Islamic Jihad.
The rockets landed near an Israeli village, setting off fires but causing no casualties.
Islamic Jihad denied involvement in Thursday's rocket salvo and said those killed in Friday's air strike were not its own.
"These are all lies ... Islamic Jihad has no armed presence outside of Palestine," group spokesman Dawoud Shehab said, referring to Israel, the Israeli-occupied West Bank and the Gaza Strip.
Islamic Jihad's leadership is based in Damascus and it has a following among Syria's Palestinian refugee community.
Israel's overnight retaliation killed one Syrian soldier and wounded seven, the Syrian army source said, although it appeared to be the fiercest Israeli bombardment for years, with dozens of raids against Syrian targets.
Israeli Prime Minister Benjamin Netanyahu said his country's forces "struck the squad that carried out the firing and the Syrian forces that enabled it to (do so)".
He also accused Iran of ordering Thursday's rocket bursts, underlining Israeli concern that a nuclear deal between Tehran and six world powers had emboldened the Islamic Republic.
"Those countries hastening to embrace Iran should know that an Iranian commander gave sponsorship and instruction to the squad that fired on Israel," Netanyahu said in a statement.
Defense experts who track Syria said the Israeli raids on Thursday were the strongest attacks on Syrian army targets in the course of Syria's four-year-old civil war.
Israeli media said the overnight exchange was the first shelling of Israeli targets from Syria since the 1973 Middle East war, and the most intensive Israeli shelling of Syria since then as well.
Previous Israeli attacks have mainly targeted supply routes and arms depots of Syrian President Bashar al Assad's Lebanese Shi'ite militant ally Hezbollah inside Syria.
Israeli Defense Minister Moshe Yaalon said the rocket flurry from Syria arose from a more aggressive Iranian policy following the July 14 nuclear deal between Tehran and the West, and he challenged the Iranians not to test "our determination".
"What we’ve seen overnight is the prelude of things to come, following the signing of the nuclear agreement and the lifting of sanctions," Yaalon said.
Israel, widely believed to hold the region's only nuclear arsenal, resolutely opposes the nuclear accord, saying Tehran is determined to acquire its own nuclear weapons and will also now have more access to funds to spread its influence in the region.
The Islamic Republic says its nuclear program is peaceful.
Separately, the Israeli army said its air and artillery strikes hit 14 Syrian military sites on the Syrian Golan.
Israel captured the western Golan in the 1967 Middle East war and annexed it, a move not recognized internationally.
Lebanese Hezbollah's Manar television said the Israeli raids targeted Brigade 90, one of the biggest Syrian army bases in the country with several rockets.
The Syrian army, on an official war footing with Israel for decades, has deployed a substantial part of its land forces and artillery in southern Syria and in the Golan Heights and built elaborate defenses against Israel.
Rebel sources said at least 50 raids targeted the main army outposts in the region including an attack on the city of Baath, the administrative capital of the Quneitra region.
Many parts of the Syrian Golan Heights have fallen under rebel control, with groups including the Syrian al Qaeda offshoot, Nusra Front, having a strong presence in the area.
A major Syrian offensive helped by Iran-backed Hezbollah to wrest back territory has failed to make inroads.
Additional reporting by Nidal al-Mughrabi in Gaza; Writing by Dominic Evans; Editing by Mark Heinrich