Turkey said Tuesday its army and allied rebels have surrounded the Kurdish city of Afrin in northern Syria, raising the prospect of another devastating siege in the country's long conflict.
Syria's war enters its eighth year this week with clashes raging on several fronts, including Afrin and the besieged rebel pockets of Eastern Ghouta, which saw their first medical evacuations of civilians on Tuesday.
While attention in recent weeks has focused on a ferocious regime assault on Ghouta, Turkish forces and allied Syrian rebels have steadily advanced against the northern Kurdish enclave of Afrin.
In a statement Tuesday, the Turkish military said it had completely encircled Afrin city, home to some 350,000 people and defended by a well-armed Syrian Kurdish militia, the People's Protection Units (YPG).
Birusk Hasakeh, a YPG spokesman inside Afrin, denied the city had been totally besieged but said the last route leading out of it was being shelled heavily.
"If they do encircle the city, we will be ready for a long fight. We will resist," he told AFP.
The Syrian Observatory for Human Rights said Turkish forces were within firing range of that route, which leads to a pair of regime-held towns -- essentially encircling Afrin and 90 villages to its west.
The United Nations said Turkey's advance over the last 48 hours had "exacerbated" the humanitarian situation, with water and shelter in short supply.
"In Afrin town and surrounding communities, the people's situation is concerning," said the UN's humanitarian coordination office (OCHA) on Tuesday.
Sealing off Afrin city would be major for Turkey's "Olive Branch" operation, launched on January 20 and aimed at ousting the YPG, a vital partner for a US-backed coalition against the Islamic State group, but seen by Ankara as "terrorists".
The assault has worried world powers, who fear it could detract from the fight against IS and was indiscriminately hurting civilians.
"If Turkey's concerns over the border are legitimate... this absolutely does not justify the action by Turkish troops deep inside the Afrin area," French Foreign Minister Jean-Yves Le Drian said.
It remains unclear what Turkey's next move will be, but it may lay siege to Afrin while allowing civilians out to avoid a high-casualty offensive.
Abu Jaafar, a commander in the pro-Ankara forces waging Operation Olive Branch, said rebels were considering an "exit route" for civilians.
"We will allow civilians... to leave so they will not be hurt in case (Kurdish) fighters hold out in the villages, neighbourhoods, or buildings inside Afrin," he said.
Hundreds of civilians were seen fleeing Afrin on Monday, with cars piled high with personal belongings heading to regime-held areas further east.
Forces loyal to President Bashar al-Assad have meanwhile been pressing an assault against Eastern Ghouta, the last major rebel stronghold near Damascus.
Since February 18, Russian-backed regime forces have recaptured more than 60 percent of Ghouta, whittling down rebel territory to three isolated pockets.
The UN Security Council passed a resolution last month calling for a 30-day truce to allow for aid deliveries and medical evacuations, but the ceasefire demand went unheeded.
A five-year government siege has left hospitals too under-resourced to treat people properly and more than 1,000 people in Ghouta need to be bussed out for care, the UN has said.
On Tuesday, around 150 civilians, some sick and wounded, were evacuated from Ghouta's largest town of Douma to regime-held territory.
Douma resident Umm Imad al-Ayyubi told AFP she had been waiting for two years to be brought out of Douma for medical treatment.
"I am sick and had heart surgery. I'm coming to Damascus for a follow-up," said the 65-year-old woman.
Jaish al-Islam, which controls Douma, had earlier announced some "critical medical cases" would be evacuated.
Nearly 1,200 civilians have been killed since the Ghouta assault was launched.
On Tuesday, the UN Deputy High Commissioner for Human Rights Kate Gilmore voiced concern for some 125,000 children trapped in Ghouta.
"Is it not tantamount to a monstrous indifference to the suffering of children that Security Council resolutions for ceasefires are flouted?" Gilmore asked.
More than 350,000 people have died since Syria's conflict broke out in 2011. With Russia's help, Assad has retaken most of the territory he had lost in the early years of the uprising.
Syrian troops have repeatedly used siege tactics, sealing off rebel-held territory and pressing a military operation before securing an evacuation deal.
Several hundred Islamist fighters evacuated the Qadam district south of Damascus on Tuesday under such an agreement.
The government has reportedly been pursing negotiations to secure local truces or evacuations from Ghouta's three rebel-held pockets to secure the capital.
On Tuesday, rebel fire from Ghouta killed one woman and wounded five other people in Damascus.