The United Nations is warning that the lives of over one million children are at “imminent risk” ahead of an expected assault on the last rebel-held province in Syria.

At a tri-lateral summit in Iran this afternoon, the leaders of Turkey, Iran and Russia failed to agree on a ceasefire that would have delayed a full-scale attack on the city of Idlib by Syrian Government forces.

In recent days, Turkish President Recep Tayyip ErdoÄŸan has warned that an attack on the area would be a “serious massacre” and called for a ceasefire.

However, at the Summit this afternoon, Russian President Vladimir Putin and Iranian President Hassan Rouhani rejected the calls.

President Putin warned that a ceasefire would be pointless – as the militant groups in Idlib would not be a party to it.

President Rouhani meanwhile, argued that the Syrian Government must regain control over the entirety of its territory.

Meanwhile thousands of Idlib residents have taken to the streets for a series of mass rallies calling on the international community to prevent the assault and denouncing Syrian President Bashar al Assad.

"Massacre"

Turkey has already taken in 3.5 million refugees from the Syria conflict – and President Erdogan said the country could take no more if an assault goes ahead.

"Whatever reason there is an attack that has been made or will be made will result in disaster, massacre and humanitarian drama," he said.

"Millions will be coming to Turkey's borders because they have nowhere to go. Turkey has filled its capacity to host refugees."

Children

In a statement this afternoon, UNICEF warned that Idlib is full of thousands of children who were forced to leave their homes by the conflict – and are now living in “overcrowded makeshift shelters, with food, water and medicine in dangerously short supply.”

The agency said it is “gravely concerned that potential airstrikes, ground military operations, and the use of explosive weapons in densely populated areas will be disastrous for children.”

“A fresh wave of violence could leave them trapped between fighting lines or caught in the crossfire, with potentially fatal consequences,” said Henrietta Fore, UNICEF Executive Director.

“Our request is simple: Protect children.

“Give us safe, sustained and unconditional access to them. Allow and enable those who want to leave to do so safely and voluntarily.”

A number other humanitarian organisations have also warned that the lives of millions are in grave danger in Idlib.

Eight aid agencies have called on world leaders to prevent a humanitarian catastrophe in the region.

The agencies, including CARE, Mercy Corps and the International Rescue Committee, said the "most vulnerable" are likely to pay the heaviest price in case of an offensive.

Military solution

Following the Tehran Summit, the three leaders adopted a statement which reaffirmed their conviction that there can be no military solution to the Syrian conflict – with a negotiated political process the only hope for peace.

However, the statement confirmed their intention to continue operations to ultimately eliminate terrorist groups in the area – including ISIS, the Al-Nusra Front and groups associated with Al-Qaeda.

The statement notes that separating the terrorists groups from rebels that would agree to a ceasefire would be of utmost importance, “including with respect to preventing civilian casualties.”

Humanitarian aid

The statement also calls on the international community, especially the UN, to step up its humanitarian aid to the country and help restore “basic infrastructure assets, including social and economic facilities, and preserving historical heritage.”

It also reaffirmed the country’s determination to protect civilians and improve the humanitarian situation by “facilitating rapid, safe and unhindered humanitarian access to all Syrians in need.”

The Syrian government was not directly represented at the summit, nor was the US or other Western powers.

It is believed Idlib’s rebel factions are divided between Tahrir al-Sham - a jihadist alliance that hold the most ground in the area - and a new Turkish-backed alliance, known as the National Liberation Front (NLF).

The NLF includes a range of different factions - including some that previously fought under the banner of the Free Syrian Army.