The mother-in-law of one of a Lebanese man and Australia's most notorious Islamic State fighters has pleaded for the government to help her "desperate" daughter and five grandchildren flee the Middle East, saying she made "the mistake of a lifetime.”

Karen Nettleton's emotional appeal for help came after reports that her son-in-law Khaled Sharrouf and his friend Mohamed Elomar were killed in fighting in the Iraqi city of Mosul in the past week, although officials Wednesday suggested they may have died in Syria .

Islamic State group spokesman Abu Mohammed al-Adnani called on Tuesday for Muslims to engage in jihad and become martyrs during the holy fasting month of Ramadan.

Adnani also announced an amnesty for people who fought against IS in Iraq's Anbar province, and called on residents who had fled violence there to return home.

A French court on Tuesday threw out a case brought by a mother trying to sue the government for failing to stop her teenage son from leaving to join jihadists in Syria.

The boy was 16 when he left with three others from the town of Nice in southern France in December 2013, taking a plane to Turkey and then traveling overland to Syria. 

Officials from Iran, Iraq and Syria will meet next week in Baghdad to strengthen their joint fight against the Islamic State jihadist group, media reports said Tuesday.

Representatives of the three countries "will have a meeting next week in Baghdad to reinforce their cooperation in the fight against terrorism," Ali Akbar Velayati, foreign affairs adviser to Iranian supreme leader Ayatollah Ali Khamenei, said Tuesday.

U.N. investigators on Tuesday denounced the seemingly deliberate targeting of civilians in Syria's war, causing "unspeakable suffering" as barrel bombs relentlessly drop from the sky and besieged people starve to death.

"Civilians are the main victims of an ever-accelerating cycle of violence," Paulo Pinheiro, who heads a commission of inquiry on the human rights situation in Syria, told the U.N. Human Rights Council.

Israeli Prime Minister Benjamin Netanyahu pledged Tuesday to track down Druze rioters in the occupied Golan Heights responsible for the "lynching" of a wounded Syrian being transported to a hospital.

The Monday attack, roundly condemned by local Druze religious and secular leadership, comes as Druze are increasingly concerned over the fate of their brethren in Syria after attacks by rebels there. 

Six Syrian migrants were killed and dozens more rescued on Tuesday when their overloaded boat capsized off Turkey's Aegean coast while on its way to Greece, the Dogan news agency reported.

The migrants were seeking to reach the Greek island of Kos and enter the European Union when their boat hit trouble in stormy weather before dawn on Tuesday after leaving the Turkish resort of Bodrum.

Syrian Kurds and allied rebels advanced against the Islamic State group on Tuesday, capturing a strategic town a day after seizing a base from the jihadists near their Raqa bastion.

A spokesman for the Kurdish People's Protection Units (YPG) and a Britain-based monitor said anti-IS forces took Ain Issa after capturing the nearby Brigade 93 base overnight.

Reports that a Lebanese-Australian terrorist, notorious for holding up the severed heads of Syrian victims, has been killed fighting in Iraq have raised the potential for his young family to be repatriated from the Middle East, Australia's foreign minister said on Tuesday.

Australian intelligence agencies were attempting to verify the recent deaths of Australians Khaled Sharrouf and Mohamed Elomar in the Islamic State-held city of Mosul in Iraq, Foreign Minister Julie Bishop said. Both men were seen in photographs posted on social media holding heads of Syrians.

A U.S. airstrike in northern Iraq has killed an Islamic State operative who was a person of interest in the 2012 Benghazi attack, the Pentagon said Monday.

Pentagon spokesman Colonel Steve Warren said Ali Awni al-Harzi of Tunisia was killed in Mosul on June 15.