Turkey called Tuesday for a ground operation with its international allies to end the war in Syria, as the United Nations announced aid convoys are being sent to besieged towns.
"So far I understand that the government of Syria has approved access to seven besieged areas," said Vanessa Huguenin, spokeswoman for the UN Office for the Coordination of Humanitarian Affairs (OCHA).
In Damascus, UN envoy Staffan de Mistura said aid convoys will be sent on Wednesday to test the resolve of warring parties to allow in humanitarian supplies.
"It is clear it is the duty of the government of Syria to want to reach every Syrian person wherever they are and allow the UN to bring humanitarian aid, particularly now after so long time," he said after meeting Foreign Minister Walid Muallem.
"Tomorrow (Wednesday) we test this," he said, referring to the warring parties.
A Red Crescent source said the first convoys will head for the rebel-besieged Shiite villages of Fuaa and Kafraya in the north, and to Madaya and Zabadani which are encircled by the army.
Around 486,700 people in Syria are in areas besieged by either government or rebel forces, UN figures show.
Scores are reported to have died of malnutrition or because of a lack of medical treatment.
On the international front, tensions escalated over Russia's air war backing Syrian President Bashar al-Assad, with Ankara branding the bombing "barbaric".
Turkey sees Assad's ouster as essential to ending a five-year conflict that has killed more than 260,000 people, and is highly critical of Iran and Russia for supporting the Damascus regime.
"We want a ground operation with our international allies," a senior Turkish official told reporters in Istanbul, adding such an operation would require the involvement of the United States and Gulf states.
- Fears of escalation -
"There is not going to be a unilateral military operation from Turkey to Syria," the official emphasised, but added: "Without a ground operation it is impossible to stop the fighting in Syria."
Saudi Arabia, another fierce critic of Assad, has said it is ready to send special forces to Syria to take part in ground operations against the Islamic State (IS) jihadist group.
On Tuesday, the Pentagon said Saudi Arabia, which has been focused on the war in its neighbour Yemen, has resumed participation in air strikes by the US-led coalition against IS in Syria.
Iranian Foreign Minister Mohammad Zarif warned Riyadh not to deploy troops in Syria, saying that without the authorisation of Damascus it would violate international law.
The Islamic republic is a key Syrian ally and has sent thousands of "military advisers" to help Assad's regime.
The UN said Monday nearly 50 civilians, including children, had died in the bombings of at least five medical facilities and two schools in northern Syria.
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The region around Syria's second city of Aleppo has been the target of a major anti-rebel offensive by government forces backed by Russian warplanes, sending tens of thousands fleeing to the Turkish border.
Russia denied it had bombed any hospital, calling such reports "unsubstantiated accusations".
De Mistura and Muallem met in the Syrian capital to try to keep alive a proposal announced in Munich last Friday for a "cessation of hostilities" in Syria within a week.
Assad has said it would be "difficult" to implement a truce by Friday. "Who is capable of gathering all the conditions and requirements in a week? No one," he said.
Turkey shelled Kurdish positions in northern Syria for a fourth straight day Tuesday, the Syrian Observatory for Human Rights said.
It said shells hit the town of Tal Rifaat which was captured on Monday from mostly Islamist rebels by a Kurdish-Arab coalition known as the Syrian Democratic Forces.
The UN Security Council on Tuesday criticised Turkey for its bombardment of northern Syria, in a decision applauded by Syria's UN ambassador.
"Turkey is trying to pull everybody into this nightmare, into this escalation," Bashar Jaafari said.
- Victory imminent: Hezbollah -
Ankara accuses the Kurdish forces of ties to the outlawed Kurdistan Workers' Party (PKK) that has waged a decades-long insurgency against Turkey.
It fears the Kurds will be able to create a contiguous Kurdish territory just across the border in northern Syria.
Turkish Prime Minister Ahmet Davutoglu on Tuesday accused Kurdish fighters in Syria of being "Russia's legion working as mercenaries", with the of harming Turkey's interests.
Russia's air strikes have allowed government forces to press a major operation that has virtually encircled rebels in eastern Aleppo city, as well as expelled them from much of the region to the north.
The head of Lebanon's Shiite movement Hezbollah which has been fighting alongside Assad's forces, declared Tuesday that "victory" was imminent.
"In the days ahead and for the decade to come... we will proclaim victory alongside the Syrian army," Hassan Nasrallah said in a video message to supporters in Beirut.
He also accused Saudi Arabia and Turkey of dragging the whole region into a war.
Turkey has been infuriated by the Kurdish advances, focusing its anger on Russia's air support.
"Those vile, cruel and barbaric planes have made close to 8,000 sorties since September 30 without any discrimination between civilians and soldiers, or children and the elderly," Davutoglu said.
On the ground, the Observatory said at least 15 civilians were killed in US-led coalition air strikes on the IS-controlled town of Al-Shadadi in Hasakeh province of northeast Syria.