KUCUK KENDIRCILER, Turkey -- The 19-year-old Kurdish militant, who has been fighting the Islamic State group in Syria, brought his family across the border into Turkey to safety Sunday. But in the tranquility of a Turkish tea garden just miles from the frontier, Dalil Boras vowed to head back after nightfall to continue the fight.

Pulling a wad of Syrian bills from his pocket, the young fighter -- who has already lost a 17-year-old brother to the Islamic militants' brutal advance -- said that if the Turkish border guards tried to stop him, money would persuade them.

Boras and his relatives are among some 100,000 Syrians, mostly Kurds, who have flooded into Turkey since Thursday, escaping an Islamic State offensive that has pushed the conflict nearly within eyeshot of the Turkish border.

The al-Qaida breakaway group, which has established an Islamic state, or caliphate, ruled by its harsh version of Islamic law in territory it captured straddling the Syria-Iraq border, has in recent days advanced into Kurdish regions of Syria that border Turkey, where fleeing refugees on Sunday reported atrocities that included stonings, beheadings and the torching of homes.

On Sunday, heavy clashes broke out between the Islamic State militants and Kurdish fighters only miles from the Syrian border town of Kobani, where the Islamic State group was bombarding villagers with tanks, artillery and multiple rocket launchers, said Nasser Haj Mansour, a defence official in Syria's Kurdish region.

"They are even targeting civilians who are fleeing," Haj Mansour told The Associated Press.

At a border crossing where Turkish authorities were processing the refugees, Osman Abbas said he and 20 relatives were fleeing a village near Kobani when Islamic State fighters shot one of his sons. The 35-year-old had tried to return to their home to recover valuables while the rest of the family fled.

"They took our village, they took our house, they killed my son," Abbas said. "I saw it with my own eyes."

As refugees flooded in, Turkey closed the border crossing at Kucuk Kendirciler to Turkish Kurds in a move aimed at preventing them from joining the fight in Syria. A day earlier, hundreds of Kurdish fighters had poured into Syria through the small Turkish village, according to the Britain-based Syrian Observatory for Human Rights.

Clashes broke out as Kurds trying to approach the crossing from inside Turkey scuffled with security forces, who responded with tear gas, paint pellets and water cannons. The state-run Anadolu Agency said the Kurdish protesters had hurled stones at the security forces.

Two people were seriously injured in the clashes, including one Kurdish legislator who was hospitalized, the pro-Kurdish Democratic Regions' Party said, adding that the Kurds were protesting the Islamic State group's attacks as well as the border closure.

The sound of gunfire could be heard from the Syrian side of the frontier, where refugees were piling up after authorities shut the crossing. It wasn't immediately clear whether they were unable to cross or simply waiting to see what would happen.

Despite the huge number of new refugees, Turkish authorities said they were ready to deal with the influx. The conflict has pushed more than a million Syrians over the border in the past 3 1/2 years.

"We have been prepared for this," said Dogan Eskinat, a spokesman for Turkey's disaster management agency. "We are also prepared for worse."

Boras, the young Kurdish fighter, said the lines between Kurdish and Islamic State fighters had held stable near Kobani for months, until the Islamic State group broke through in recent days, armed with more powerful weapons, including tanks. He said he did not know where the heavier weaponry came from.

Two days earlier, his 17-year-old brother was killed in fighting, he said, and another 16-year-old brother, who he had brought to Turkey with his family, slipped back over the border Sunday. The three brothers were fighting with the YPK military wing of Syria's Kurdish Democratic Union Party. Turkey is wary of YPK militants, who it believes are affiliated with the PKK movement, which waged a long and bloody insurgency in southeast Turkey.

Boras said the Islamic State has been killing indiscriminately as they rolled through villages and that he had seen the devastation, which included blowing up houses with gasoline bombs.

"They captured women, buried them to the neck and stoned them," he said.

Late Sunday, the AP reached Boras in Syria by cellphone. He said he was heading back toward Kobani to recover his weapons and return to the front lines.

While his report about atrocities could not be independently verified, the situation on the Syrian side of the border is dire.

The Britain-based Syrian Observatory for Human Rights said the Islamic State group has taken control of 64 villages in northern Syria since the fighting began there early Wednesday. It says that the fate of 800 Kurds from these villages is unknown, adding that the Islamic State group had killed at least 11 civilians, including two boys.

The Aleppo Media Center, another activist group, said that Sunday's battles were concentrated on the southern and eastern suburbs of Kobani. Mansour said the battles are taking place about eight miles (13 kilometres) from the town.

Mohammed Osman Hamme, a middle-aged Syrian Kurdish refugee who managed to make his way into Turkey, told the AP he fled with his wife and small children from the village of Dariya in Syria's Raqqa province 10 days ago after hearing that the Islamic State group was headed their way.

The family walked for three days, passing the town of Tal Abyad, near the Turkish border, where they saw four severed heads hanging in the streets, he said.

As he spoke a tear gas gun went off, causing Hamme's terrified daughter to start screaming. Later, Turkish police used armoured cars to push people back from the border crossing at Kucuk Kendirciler.

UNHCR spokeswoman Selin Unal said most of those coming across the border are Kurdish women, children and the elderly.

She urged the international community to step up aid for Syrian refugees in Turkey.

"Turkey is assisting with all needs but it's huge numbers," she said.

Associated Press writers Suzan Fraser in Ankara, Bassem Mroue in Beirut, and Frank Jordans in Berlin, contributed to this report.