The mother-in-law of a notorious Lebanese-Australian Islamic State group fighter said Monday she was "devastated" that police had refused to help bring her five grandchildren home from Syria.

Karen Nettleton's daughter Tara is married to Khaled Sharrouf, who gained global infamy last year when he posted pictures of himself and his seven-year-old son on Twitter holding up the severed heads of soldiers.

A rebel mortar attack killed four civilians on Sunday in the Syrian capital as government forces battled Islamic State group jihadists in the northern city of Hasakeh, a monitor said.

The Syrian Observatory for Human Rights said a mortar round struck Revolution Street in central Damascus, killing four people and wounding 13.

The Islamic State group has executed more than 3,000 people in Syria, including hundreds of civilians, in the year since it declared its self-described "caliphate," a monitor said on Sunday.

The Syrian Observatory for Human Rights, a Britain-based group monitoring Syria's conflict, said it had documented 3,027 executions by IS since June 29, 2014.

Mohammed Nasif Khayrbik, a senior Syrian government security official close to President Bashar Assad, died on Sunday morning after a long illness, state media said.

Khayrbik was a key confidante of the Assad family and the target of EU and U.S. sanctions for his alleged role in putting down anti-government demonstrations and interfering in neighboring Lebanon.

Twelve students including British, Canadian, Sudanese and U.S. citizens are feared to have traveled from Khartoum to Turkey to try to join the Islamic State (IS) group, their university's dean told AFP Sunday.

Another group of British students of Sudanese origin from the same private University of Medical Sciences and Technology traveled to Turkey in March and it is believed they crossed into Syria.

Defense Minister Samir Moqbel assured on Sunday that the army is in full control of the situation on the borders and inside Lebanon, in the wake of reports that terrorist acts could spread to the Lebanese arena.

“The army is in control of the situation whether at the borders or inside Lebanon's territories. The army is carrying out its duties and there is no fear of the Islamic State or of any other,” said Moqbel to al-Mustaqbal daily.

Canberra was Sunday attempting to verify whether an Australian Islamic State group fighter, notorious for being photographed with severed heads, had survived a drone attack after a report said he was still alive.

Australian media last week reported that two of the country's most wanted IS jihadists, Khaled Sharrouf and Mohamed Elomar, were believed killed in a drone strike in Syria.

Turkish President Recep Tayyip Erdogan said that Turkey will never allow the establishment of a Kurdish state in Syria after major gains by Kurdish fighters.

In a strong-worded warning late on Friday, Erdogan accused the Kurds of ethnically cleaning other communities from land they have taken after pushing back Islamic State forces from the Turkish border.

The Lebanese army succeeded on Friday in thwarting six gunmen from entering Lebanon through the northeastern border town of Arsal, killing two, while the rest escaped, revealed al-Joumhouria newspaper on Saturday.

A military source told the daily: “The army is tightening the noose around the gunmen on Arsal's outskirts.”

France and Spain pledged Friday to launch a new effort at the U.N. Security Council for action to stop barrel bomb attacks in Syria, which rights groups describe as a leading killer in the war.

The council adopted a resolution in February 2014 demanding an end to the bombings that the West says are carried out by the Damascus regime using helicopters to drop barrels rigged with explosives on civilian districts.