A military aircraft circles above Kobani, Syria, seen from a hilltop on the outskirts of Suruc, at the Turkey-Syria border, Thursday, Oct. 23, 2014. Kobani, also known as Ayn Arab, and its surrounding areas, has been under assault by extremists of the Islamic State group since mid-September and is being defended by Kurdish fighters. (AP Photo/Vadim Ghirda)
Thick smoke and flames from an airstrike by the U.S.-led coalition rise in Kobani, Syria, as seen from a hilltop on the outskirts of Suruc, at the Turkey-Syria border, Monday, Oct. 20, 2014. Kobani, also known as Ayn Arab, and its surrounding areas, has been under assault by extremists of the Islamic State group since mid-September and is being defended by Kurdish fighters. (AP Photo/Lefteris Pitarakis)
Thick smoke from an airstrike by the US-led coalition rises in Kobani, Syria, as seen from a hilltop on the outskirts of Suruc, at the Turkey-Syria border, Wednesday, Oct. 22, 2014. Kobani, also known as Ayn Arab, and its surrounding areas, has been under assault by extremists of the Islamic State group since mid-September and is being defended by Kurdish fighters. (AP Photo/Lefteris Pitarakis)
MURSITPINAR, Turkey — U.S.-led coalition airstrikes in Syria have killed more than 500 people since they began last month, mainly Islamic militants, activists said Thursday, as fighting flared yet again in the northern Syrian border town of Kobani.
Despite the large death toll and international intervention to aid Kurdish forces fighting to defend Kobani, Islamic State forces on Thursday seized a hilltop overlooking the town along the Syria-Turkey border, activist said.
To aid their brethren, Iraqi Kurds pledged to send dozens of fighters over the coming days to battle alongside Syrian Kurdish forces in Kobani.
The Britain-based Syrian Observatory for Human Rights, which has a network of activists on the ground, said 553 people have been killed in airstrikes since they began Sept. 23, including 32 civilians. The civilians included six children and five women.
The group said it documented 464 deaths among fighters of the Islamic State group but said the number could be much higher. Also, 57 fighters from the al-Qaida-linked Nusra Front were killed in airstrikes elsewhere in northern Syria, the Observatory said.
Many of the Islamic State fighters died in the battle for Kobani, which the militants have been trying to seize since mid-September. The IS group also captured dozens of surrounding Kurdish villages, compelling more than 200,000 people to flee to neighboring Turkey.
Earlier this week, the U.S. Central Command said its forces conducted more than 135 airstrikes against the militants in and around Kobani, killing hundreds of fighters.
"Combined with continued resistance to ISIL on the ground, indications are that these strikes have slowed ISIL advances into the city, killed hundreds of their fighters and destroyed or damaged scores of pieces of ISIL combat equipment and fighting positions," Central Command said in a statement, using one of the acronyms for the militant group.
In northern Iraq, Fuad Hussein, the chief of staff for the Kurdish regional President Massoud Barzani, told The Associated Press that the largely-autonomous Iraqi Kurdish government would send some 150 peshmerga fighters to Kobani through Turkey to support Syrian Kurds there.
Hussein said they would take light weapons and rocket-propelled grenades, and in a response to Turkish concerns about armed Kurds on their territory, said the peshmerga would bring the weapons back once they returned.
"The fight in Kobani is very important to us," he said. "We are fighting the same enemy."
On the Turkish side of the border, heavy machine gun fire was heard on Thursday coming from Kobani, also known as Ayn Arab in Arabic.
The clashes were some of the fiercest since the battle for the town began, Kurdish activist Farhad Shami said over the phone. Speaking from the area, he said the Islamic State group launched an attack from three fronts late Wednesday.
By Thursday, the militants captured the Tel Shair hill that overlooks parts of Kobani, closing in on the town from the west, the Observatory reported.
Shami said the Kurdish fighters had withdrawn from the area. The Observatory said Islamic State fighters were also trying to advance from the eastern side of the town.
Capturing Kobani would give the Islamic State group, which already rules a huge stretch of territory spanning the Syria-Iraq border, a direct link between the Syrian province of Aleppo and its stronghold of Raqqa, to the east.
NATO's supreme military commander, U.S. Air Force Gen. Philip Breedlove, said in Turkey on Thursday that the alliance was ready to come to Turkey's defense if the situation on its border deteriorated and it sought help from the organization.
He said that NATO had already provided Turkey will a Patriot missile defense system that it had deployed on the border with Syria.
"NATO is ready," Breedlove said. "We will work together to face this challenge that we see on the border."
The Observatory meanwhile reported four coalition airstrikes on oil wells in the Jafra field in eastern Syria late Wednesday.
Central Command said they had conducted six airstrikes since Wednesday; four near Kobani, and two that targeted oil-holding tanks.
The U.S.-led coalition has been shelling IS-held oil facilities in Syria, which provide a key source of income for the militants. But such strikes also endanger civilians, which could undermine long-term efforts to destroy the militant group.
The attacks on the oil industry, including refineries, have also led to a sharp rise in the price of oil products in rebel-held areas of Syria.
Meanwhile, the Syrian government of President Bashar Assad has stepped up its efforts to reclaim rebel-held areas surrounding major cities. On Thursday, state-run media said government forces wrested the town of Morek in central Syria from rebels. The town is seen as a strategic prize, because it lies on the highway between the key cities of Hama and Aleppo.
Also Thursday, neighboring Lebanon said it would not accept any more refugees from Syria, except in what authorities deem to be "exceptional" cases — a move that could prevent tens of thousands of Syrians from escaping the civil war.
There are over 3 million Syrian refugees from the war, mostly in neighboring countries. Another 6 million have been displaced within Syria, making it one of the world's worst humanitarian crises.
Lebanon itself has at least 1.1 million Syrian refugees, forming a quarter of the tiny Mediterranean country's population of 5 million. The refugees have stretched Lebanon's already fragile infrastructure and compete with the country's poorest for low-paid jobs, causing tensions. Tens of thousands of Syrian children are out of school because there is nowhere to place them.
Lebanese Information Minister Ramzi Jreij said Lebanon can simply not handle any more refugees.
Ninette Kelley, the U.N. refugee agency's representative in Lebanon, said the country had begun restricting the entry of Syrians since August.
Mroue reported from Beirut. Associated Press writers Diaa Hadid in Beirut, Patrick Quinn in Izmir, Turkey, and Bram Janssen in Irbil, Iraq, contributed to this report.