Nusra Front rebels in Daraa, southern Syria
Nusra Front rebels in Daraa, southern SyriaReuters

The family of an Israeli Arab who paraglided into Syria to join Islamist rebels there say they received a phone call - presumably from rebels - telling them their son was unharmed.

"The uncle said the young man's father had received a phone call about an hour after an (army) observation post spotted the paraglider, in which he was told, 'Your son is fine. He's with us. Don't worry,' before the call was cut off," Haaretz reported.

The paper said that the family had noticed the man becoming more intensely religious of late.  

"He started becoming more religious. He started praying every morning in the mosque," it quoted the uncle - who said he last saw the young man on Friday as saying.

"I told him that he's 23 now and the best thing he should do is get married and have children and raise a family." 

According to the Israeli army, "A surveillance post identified an Israeli civilian entering Syrian territory using a paraglider."

"The preliminary review indicates that the civilian that entered is a resident of Jaljulia," an Arab town in central Israel.

The IDF said the paraglider took off from the southern section of the Israeli Golan Heights, adjacent to southern Syria.

It challenged speculation that he may have been blown off-course and crossed the border inadvertently. "Initial investigation suggests Israeli-Arab crossed intentionally," a military statement on Twitter said.

The Al-Yarmouk Martyrs Brigade, which is supportive of the Islamic State (ISIS) terrorist group and active in the Daraa area in south Syria, addressed rumors circulating about the flight on Saturday night, stating on its Facebook page it had not taken an Israeli captive.  

Speaking at the start of his Sunday cabinet meeting, Prime Minister Binyamin Netanyahu said that he would be taking measures to strip the man of his Israeli citizenship.

"Yesterday an Israeli citizen crossed our border in the Golan Heights into Syria to join the ranks of the enemy," he said.  

"We will act to nullify his citizenship. That is what is done in any such case. Whoever joins the ranks of the enemy to fight against Israel, will not be an Israeli citizen."

According to the Shin Bet internal security agency, some 45 Arab Israelis have joined jihadist forces in Syria, mainly entering through Turkey. At least four were killed in fighting there, and 10 were arrested upon returning to Israel.  

The Shin Bet has warned of the "security threat posed by Israelis joining ISIS after being exposed to propaganda disseminated by the group, primarily via the Internet.  

"Their return to Israel, with knowledge of and practical experience in terrorism and warfare, exposes the country to significant risks of severe terrorism," the agency said in a statement earlier in the year.

AFP contributed to this report.