Some 130,000 Syrian refugees fleeing the advance of Islamic State militants have crossed the border into Turkey in the past four days, Turkey's deputy prime minister said Monday, warning that the number could rise further as the militants continue their onslaught.

Numan Kurtulmus warned that the number could rise to "a refugee wave that can be expressed by hundreds of thousands."

The refugees have been flooding into Turkey since Thursday, escaping an Islamic State offensive that has pushed the conflict nearly within sight of the Turkish border. The conflict in Syria had already pushed more than a million people over the border in the past 3 1/2 years.

'Man-made disaster'

"This is not a natural disaster... What we are faced with is a man-made disaster," said Kurtulmus, adding that Turkey was taking measures to prepare.

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Around 130,000 Syrian Kurds have been crossing into Turkey as they flee Islamic State fighters who advanced into their villages. (Burhan Ozbilici/Associated Press)

"We don't know how many more villages may be raided, how many more people may be forced to seek refuge. We don't know," he added. "An uncontrollable force at the other side of the border is attacking civilians. The extent of the disaster is worse than a natural disaster."

The situation has raised tensions between Turkish authorities and Kurds, who claim the government is hampering their efforts to help their brethren in Syria by refusing to let Turkish Kurds cross into Syria. New clashes Monday erupted along the border near the town of Suruc, with Turkish police firing tear gas and water cannons to disperse Kurds protesting the government or demanding to reach Syria.

Tony Blair: Don't rule out ground troops

Former British Prime Minister Tony Blair said on Monday ISIS can't be defeated by air strikes alone, and that the use of special forces capabilities on the ground should not be ruled out. 

Western powers must be ready to commit ground forces to the fight against militants from the Islamic State group because airstrikes alone won't defeat these "fanatical" extremists, Blair said. Writing on his Faith Foundation website, Blair said it would be better if the troops were to come from those closer to the fighting, such as Iraqi or Kurdish forces, but it may not be enough.

"There are already close to 1.4 million Syrians in Turkey, plus tens of thousands of Iraqis who have fled in recent weeks, so the situation is an extreme one," UN representative Carol Batchelor told CBC's Carol Off.

Batchelor said the numbers would be "staggering for any country to cope with."

She said the vast majority of refugees coming to Turkey were women, children and the elderly.

Turkish officials have now closed parts of the border, Batchelor said, in a bid to "streamline" the process as people poured into the country.

"Refugees were coming across about nine different crossing locations," she said. "Authorities wanted to streamline so that they could do security checks, medical checks — proper processing of people. So they've reduced the locations at which people can cross."

Security was an "additional element" along the border, she said, noting that over the weekend mortar and shelling could be heard roughly 500 metres from the border.

"The authorities are trying to manage the security at the border, while at the same time they say they remain committed to ensuring that civilians who have to flee to save their lives will be admitted to Turkey."

'Uncontrollable force'

Refugees on Sunday reported atrocities by Islamic fighters that included stonings, beheadings and the torching of homes.

"We don't know how many more villages may be raided, how many more people may be forced to seek refuge," Kurtulmus said. "An uncontrollable force at the other side of the border is attacking civilians."

Suruc itself was flooded with refugees and armoured military vehicles.

The al-Qaeda breakaway group — which says it has established an Islamic state, or caliphate, ruled by a harsh version of Islamic law in territory it captured straddling the Syria-Iraq border — has recently advanced into the Kurdish regions of Syria that border Turkey.

Turkey had previously been reluctant to take part in international efforts against the group, citing the safety of 49 citizens taken hostage in June when the Islamic group overran the Iraqi city of Mosul. But on Saturday, Turkey secured the hostages' release but would not say how. President Recep Tayyip Erdogan has denied paying a ransom but has been vague on whether there was a prisoner swap.

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Syrian Kurds have been forced to flee to Turkey in the face of an ISIS advance. (REUTERS)

U.S. Secretary of State John Kerry said Monday the United States now expects Turkey to step up in the fight against the militants.

Fighting raged Monday between Kurdish fighters and the militants near the northern Syrian city of Kobani, the Britain-based Syrian Observatory for Human Rights said. Parts of the city are within a mile of the Turkish border.

The Observatory said the militants have lost at least 21 fighters since Sunday night, most of them on the southern outskirts of Kobani.

Nawaf Khalil, a spokesman for Syria's Kurdish Democratic Union Party, or PYD, told The Associated Press the situation on the ground "is better than before." He said the main Kurdish force in Syria, the People's Protection Units, had pushed Islamic State fighters 10 kilometres away from previous positions east of Kobani.

"We will fight until the last gunman in Kobani," Khalil said.