The head of the U.N. cultural organization on Wednesday called for a campaign against the "culture cleansing" being carried out by Islamic State jihadists.

"Extremists don't destroy heritage as a collateral damage, they target it systematically to strike societies at their core," Irina Bokova said in a speech at the Chatham House think tank in London.

Turkish authorities on Wednesday arrested seven men suspected of fighting alongside the Islamic State (IS) group in Syria, state media reported.

The suspects were arrested in raids in the western city of Izmir, southern city of Isparta and in eastern Erzurum province, Anatolia news agency said.

A Syrian rebel group operating around Damascus has executed 18 alleged members of the Islamic State group in a video mimicking the extremist organisation's own productions.

The video, which emerged overnight, shows fighters from Jaysh al-Islam (Army of Islam) wearing the orange prison clothes that IS victims often sport.

Syrian Kurdish forces regained full control of Tal Abyad on Wednesday, expelling Islamic State group fighters who had seized a district of the strategic border town, a monitor said.

"Kurdish fighters expelled IS from the Mashur al-Fawqani district that they had captured yesterday (Tuesday)," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.

Germany's domestic intelligence agency has warned that Hizbullah has 950 active operatives in the country while Islamist Movement Hamas, which rules the Gaza Strip, has 300.

The agency (BfV) did not give further details on Hizbullah's alleged operations in Germany but said the country “is on the spectrum of goals for Islamic terrorists.”

An Australian man has died after stepping on a landmine in Syria while fighting for Kurdish forces against the Islamic State group, his family said Wednesday.

Keith Harding said he learned on Monday that his 23-year-old son Reece, who left Australia in May, died on the weekend during a night-time operation.

A U.N. envoy who has spent two months meeting with key players in Syria will address the Security Council next week to make recommendations for ending the war.

Staffan de Mistura will be in New York from Monday to meet with Secretary-General Ban Ki-moon and brief the 15-member council, U.N. spokesman Farhan Haq said Tuesday.

Islamic State group fighters re-entered Syria's Tal Abyad Tuesday, seizing a district from the Kurdish forces who captured the border town in a key victory two weeks ago, a monitor said.

"A cell of Islamic State fighters infiltrated Tal Abyad and took control of a district in the eastern outskirts of the town," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

Turkey sought to calm speculation Tuesday it was planning to invade Syria, saying it would not act unilaterally but has a right to protect its borders.

"To interpret our border security measures as 'Turkey is going to war'... is not very rational," presidential spokesman Ibrahim Kalin told a press conference in Ankara.

Norwegian prosecutors are seeking an eight-year jail sentence for a jihadist who they say fought for the Islamic State group and an affiliate of al-Qaida in Syria, media reported Tuesday.

The 24-year-old Norwegian, named as Ishaq Ahmed by the TV2 channel, left for Syria in October 2013. Prosecutors say he fought for IS before joining the al-Nusra Front, al-Qaida's Syrian affiliate.