A heavy fall of snow on Wednesday caused travel chaos in Istanbul, forcing the temporary closure of Turkey's main airport and causing hundreds of traffic accidents.

Istanbulites woke up to find the famed minarets and domes of the historic city's skyline layered in snow after a heavy fall overnight that has still shown no sign of abating.

Turkey's ruling party on Wednesday struggled to push a hugely controversial bill boosting the powers of police against protesters through parliament, after tensions spilled over into fighting between MPs that left five deputies hurt.

The scuffles overnight Tuesday to Wednesday -- some of the worst seen in the national assembly in years -- saw MPs brandishing ceremonial gavels, exchanging punches and one deputy even dumped in a flowerbed.

Decked out in his U.S. army-issued fatigues and a lip stud shining from his mouth, the young American fighter cuts an unusual figure in the northern Iraqi town of Al-Qosh.

He served in the U.S. army in Baghdad in 2006-2007 and has now returned to fight the Islamic State jihadist group with Dwekh Nawsha, a Christian militia whose name is an Assyrian-language phrase conveying self-sacrifice.

The United States and Turkey have agreed "in principle" on a deal to train and equip Syrian rebel forces, the State Department said Tuesday.

"As we have announced before, Turkey has agreed to be one of the regional hosts for the train-and-equip program for moderate Syrian opposition forces," department spokeswoman Jen Psaki told reporters. 

Turkey lashed out Tuesday at Armenian President Serzh Sarkisian for his decision to withdraw from parliament a landmark deal aimed at repairing relations between the two nations. 

"We don't think this is the right approach by Armenia, it is an erroneous and baseless step," said Turkish foreign ministry spokesman Tanju Bilgic in Ankara, quoted by Turkish media.

Turkey has stepped up arrests of activists accused of personally insulting President Recep Tayyip Erdogan, detaining at least four people in the last four days on charges of slandering the Turkish strongman, reports said Tuesday

The opposition accuses the authorities of setting up a cult of personality around Erdogan, who moved to the presidency in August after over a decade as prime minister.

The Turkish parliament Tuesday was to start debating a contentious security bill boosting police powers which activists fear will create an effective police state under President Recep Tayyip Erdogan.

The so-called "homeland security reform" bill was submitted to parliament by the ruling Islamic-rooted Justice and Development Party (AKP) after deadly pro-Kurdish protests in October.

Anger mounted in Turkey Monday over the murder and attempted rape of a 20-year-old female student by a bus driver, as a court placed three suspects in pre-trial detention over the brutal killing.

The killing of Ozgecan Aslan, 20, has within days become a rallying cause for activists campaigning to end the country's endemic levels of violence against women, with thousands taking to the streets to protest over the weekend.

Women's rights activists in Turkey took to the streets on Saturday in protest at the murder of a young woman after she resisted an alleged attempt to rape her, local media reported.

Hundreds of women gathered in Istanbul's Taksim square chanting slogans such as "You will never walk alone!".

Secular Turks opposed to President Recep Tayyip Erdogan on Friday boycotted schools and took to the streets to demand a secular education and denounce a claimed creeping Islamisation of the schools system.

The protests were led by Turkey's largest religious minority the Alevis, who adhere to an offshoot of Shia Islam, as well as leading education union Egitim Sen.