The U.N. human rights chief on Thursday urged the Syrian authorities to release all activists, lawyers and other detainees they have been holding without due process, including some jailed for years.

U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein estimated that between tens of thousands and hundreds of thousands of people have been held at some point in government jails since the first anti-regime protests erupted in Syria nearly four years ago.

Three Syrian refugee children burned to death in a fire that destroyed their makeshift wooden hut in the northern region of Akkar on Thursday, a security services official told AFP.

The three children, two sisters and their cousin, were living in the hut built a year ago on the roof of a building in the town of Bhannine.

Something happened in prison to Omar El-Hussein, the 22-year-old identified by police as the gunman who killed two people in a weekend shooting spree in Copenhagen.

His transformation from small-time criminal to cold-blooded killer is fuelling a debate about whether a radicalised environment in Danish prisons is pushing smalltime gangsters into the arms of Islamic extremism.

Shiite Arab militias have flooded into northern Iraq's Kirkuk region to help Kurdish forces battle the Islamic State group, but their uneasy alliance threatens to reignite a much older conflict over the oil-rich area pitting the largely autonomous Kurds against the Arab-led government in Baghdad.

All across Iraq, the rapid advance by the Islamic State extremists over the past year has drawn longtime rivals into reluctant alliances. The shared struggle could with time help Iraqis forge a long-elusive sense of national unity. But it also risks papering over disputes that could burst into the open if the threat subsides.

Army Commander General Jean Qahwaji headed to the Saudi capital Riyadh to take part in a two-day meeting for military leaders from more than 20 partner nations in a U.S.-led coalition to degrade and destroy Islamic State of Iraq and the Levant (ISIL).

Qahwaji traveled on Wednesday night to Saudi Arabia.

The United States will provide basic military training and equipment to Syrian rebels and may eventually instruct them on how to call in air strikes against Islamic State jihadists, the Pentagon said Wednesday.

But for the moment, the training will focus on fundamentals and not the more complicated task of directing U.S.-led warplanes to a particular target, the skilled job of a forward air controller, Pentagon spokesman Rear Admiral John Kirby told reporters.

The Syrian regime is ready to suspend aerial bombardment of Aleppo to allow a humanitarian ceasefire, a U.N. envoy said, even as government troops sought to encircle embattled rebels.

The comments by Staffan de Mistura on Tuesday came as regime forces cut the main rebel supply line into Aleppo in fighting that killed more than 150 people.

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. 

Japan has granted Lebanon $18 million to help the country cater to the needs of the Syrian refugees, Tokyo's embassy in Beirut announced on Tuesday.

“In light of its concern regarding the protracting nature of the Syrian crisis and the continuous pressures on the countries that are hosting refugees, the government of Japan decided on February 3 to offer additional aid worth $18 million to Lebanon,” the embassy said in a statement.