DAMASCUS, April 23 (Xinhua) -- An Israeli shelling targeted a camp of the National Defense Forces in Syria's southern province of Qunaitera on Sunday morning, killing three soldiers, a monitor group reported.

The camp is located in the Naba al-Fawar area in Qunaitera countryside, said the Syrian Observatory for Human Rights, adding that it wasn't yet clear whether the blast was the result of a rocket fire or shelling by a warplane.

Meanwhile, eye witness told Xinhua that a big explosion was heard in the morning, afterwards a big fire broke out at the camp, which is only one km from a UN headquarters in that city, and close to the road between Qunaitera and Damascus.

The blast was followed by a rebel attack on pro-government towns in Qunaitera countryside with rocket and artillery fire.

Meanwhile, the pro-government media outlets reported the explosion, but didn't confirm whether it was an Israeli attack.

Still, it wasn't the first Israeli strike this week.

On Friday, the Israelis struck three military positions in Qunaitera, over claims of errant fire comping from Qunaitera to the Israeli-occupied Golan Heights.

It is widely believed through that Israel carries out airstrikes at weapon shipments for Hezbollah in Syria, and it had been providing medical treatment to wounded rebels who reached the border.