Seven years into Syria's conflict, fighting continues to rage on several fronts, with millions of civilians caught in the crossfire or in desperate need of humanitarian aid.
Since starting in 2011 with the brutal repression of anti-government protests, the war has evolved into a complex conflict involving international powers and jihadists.
Here is a brief overview of the main battlefronts in Syria today and who is fighting there.
- Afrin -
The latest front to open up in the war is Syria's Kurdish enclave of Afrin, which is bordered by Turkey to its west and north and surrounded by pro-Ankara rebels to its east and south.
On January 20, Turkey-backed Syrian rebels launched an offensive against Kurdish militia in the northwestern enclave.
Ankara accuses the Kurdish People's Protection Units (YPG) of being a "terrorist" offshoot of its outlawed Kurdistan Workers' Party (PKK).
But the YPG is also a key component of a US-backed Kurdish-Arab alliance fighting the Islamic State group in Syria.
Despite heavy Turkey-led air strikes and artillery fire, the operation has however advanced slowly, the Britain-based Syrian Human Rights Observatory war monitor says.
The Kurds have several times called for President Bashar al-Assad's regime to intervene to defend Afrin, but Damascus has taken no military action so far. The president has condemned "brutal Turkish aggression".
Since January 20, the fighting has killed 77 Syrian civilians including 21 children, the Observatory says.
At least 15,000 people have been displaced in the area, the United Nations says.
- Eastern Ghouta -
Eastern Ghouta, the last rebel stronghold outside the capital Damascus, has come under heavy regime air strikes and artillery fire in recent weeks.
Last week, in just five days, regime bombardment on the besieged region killed more than 250 civilians and wounded over 770 others, the Observatory says.
That came despite Eastern Ghouta being one of four "de-escalation zones" agreed last year by regime allies Russia and Iran, as well as rebel backer Turkey, to stem fighting around the country.
Jaish al-Islam, a powerful Islamist rebel group that has recognised the de-escalation deal and taken part in UN-backed peace talks, is among the most powerful groups in Eastern Ghouta.
It controls Douma, the largest city in the region, but shares power with Faylaq al-Rahman, another Islamist rebel group that controls the localities of Erbin and Hammuriyeh.
Government forces have slowly eaten away at opposition-held territory east of Damascus in recent years, leaving the rebels in control of just around 100 square kilometres (less than 40 square miles).
Rebels regularly fire rockets into the regime-controlled capital.
Some 400,000 people live in the enclave, where they have been under siege by the army since 2013, facing severe food and medicine shortages.
In November, the United Nations reported an alarming rate of child malnutrition there, which it said was the worst in all of Syria's war.
Syria's conflict has killed more than 340,000 people since 2011, with the de-escalation zones -- including in the northwestern province of Idlib -- failing to stem the fighting.
- Idlib -
On December 25, regime forces backed by Russian air power launched an operation on Idlib, the last province in Syria outside regime control.
The offensive aimed to seize parts of the province from Hayat Tahrir al-Sham (HTS), an alliance dominated by Al-Qaeda's former Syrian affiliate.
Seeking to secure a route from Aleppo city to Damascus further south, they have since advanced inside the province and seized the key military airport of Abu Duhur.
Jihadists and rebels overran Idlib in 2015, but since then, hardliners have expanded their control and the influence of mainstream rebels has shrunk drastically.
Some 2.5 million people, including more than one million displaced Syrians, live in the province.
- Deir Ezzor -
In the eastern province of Deir Ezzor, the Islamic State jihadist group has lost almost all of the territory it once controlled to two separate offensives.
Russia-backed regime forces control the west side of the Euphrates River that cuts across the province.
And a US-backed Kurdish-Arab alliance, the Syrian Democratic Forces, is stationed on the river's eastern bank.
A "deconfliction zone" has been set up by Russia and the United States along the river to avoid clashes between both sides, but last week the US-led coalition said SDF fighters had killed more than 100 loyalists. Pentagon chief Jim Mattis said it was an act of "self-defence".
Holed up in their last hideouts, IS fighters sporadically carry out attacks on their adversaries.