SURUC, Turkey » Fierce fighting Monday between the Islamic State militant group and Kurdish forces just over the border in Syria brought the battle closer to Turkey, triggering a surge of tens of thousands of refugees and raising pressure for the government to step up efforts to take on the Sunni extremists. Meanwhile, the United States and five Arab countries launched the first airstrikes in Syria against Islamic State fighters.

The Islamic State group’s offensive against the Syrian city of Kobani, a few miles from the border, has sent 130,000 refugees to seek safety in Turkey in the last few days. The conflict in Syria had already led to more than 1 million people flooding over the border in the past 3 1/2 years.

As the fighting intensified near the Turkish border, the Pentagon said a mix of manned aircraft fighter jets and bombers plus Tomahawk cruise missiles fired from U.S. ships in the northern Persian Gulf and the Red Sea targeted the Islamic State group in Syria.

U.S. officials said the airstrikes began around 2:30 p.m. Hawaii time, and were conducted by the U.S., Bahrain, Qatar, Saudi Arabia, Jordan and the United Arab Emirates. The first wave of strikes finished about 90 minutes later, but the operation was expected to continue for several more hours, according to one U.S. official, who spoke on condition of anonymity because he was not authorized to speak publicly by name about an ongoing mission.

Because the military operation was ongoing, no details could be provided yet, said Rear Adm. John Kirby, the Pentagon’s press secretary. He said the military made the decision to strike early Monday. A White House official said Obama was being updated.

Some of the airstrikes were against Islamic State group headquarters in Raqqa in eastern Syria. Military officials have said the U.S. would target militants’ command and control centers, re-supply facilities, training camps and other key logistical sites.

The strikes were part of the expanded military campaign that President Barack Obama’s authorized nearly two weeks ago in order to disrupt and destroy the Islamic State militants, who have slaughtered thousands of people, beheaded U.S. and British captives, and captured a large swath of territory in Syria and Iraq. The U.S. has already launched 190 airstrikes on Islamic State targets in Iraq since an aerial campaign began Aug. 8.

As the Islamic State fighters pushed into Kurdish territory in Syria near the Turkish border, the government in Ankara is facing increasing pressure to step up efforts to take on the Islamic State extremists.

Turkey is resisting because it fears that arming Kurdish men to fight the group could complicate peace talks with Turkish insurgents within its own borders.

The Islamic State group’s offensive against the Syrian city of Kobani, a few miles from the border, has sent 130,000 refugees to seek safety in Turkey in the last few days. The conflict in Syria had already led to more than 1 million people flooding over the border in the past 3 1/2 years.

But in addition to the refugee crisis, hundreds of Kurds in and around this city near the frontier have clashed with Turkish police, who fired tear gas and water cannons. The Kurds say Turkey is hampering their efforts to let them cross into Syria and help their brethren.

An 18-year-old Turkish citizen in Suruc said he wanted to join the Kurdish fighters in Syria. He identified himself only by his first name of Azam for fear of reprisal from authorities.

"The Islamic State is on the other side of the border and moving freely, slaughtering people, but they are just sitting and watching," he said of the Turkish authorities.

"If I get a chance to get a weapon, I’ll go to help our brothers by end of the day," he said. "Kobani is our land, too, and people there are our people."

Syrian Kurdish fighters were crossing back and forth over the border, while other Syrian Kurds were seen selling livestock to raise money for weapons.

Not far away on the border, the black flag of the Islamic State could be seen flying in a captured Syrian village along with the smoke from mortar fire.

Spillover from the Syria poses a problem for Turkey. The only local fighters capable of resisting the Islamic State group are Syrian Kurds aligned with the Kurdistan Workers’ Party, or PKK, which has fought a three-decade insurgency in southeastern Turkey.

Turkish officials have said PKK militants from Turkey are streaming to Syria to join the fight. The conflict in Syria already is inflaming tensions with Turkish Kurds and could undermine peace talks with the PKK. Turkey’s ambivalence about the fight between Kurds and the Islamic State group, which could leave the PKK either drained or emboldened, could further complicate its participation in a U.S.-led coalition against the Islamic State group.

While joining the coalition, Turkey had declined to take part in combat, citing the Turkish hostages held by the Islamic State group in Mosul, Iraq. But even after the 46 Turks and three Iraqis were freed, Turkey has not changed its stance.

Turkish government officials have not revealed how they managed to secure the release of the captives. President Recep Tayyip Erdogan denied paying a ransom but has been vague on whether there was a prisoner swap.

Erdogan indicated for the first time Monday that his country may have traded Islamic State group prisoners it held captive in exchange for the Turkish hostages held by the militants.

Asked about it in New York on Monday, Erdogan said "such things may be possible." He said Israel released 1,500 Palestinian prisoners in exchange for one Israeli hostage. "So you see, it’s possible," he added.

Speaking at the Council of Foreign Relations in New York, Erdogan tried to sidestep the question.

"This process that took 102 days involved an operation by the national intelligence agency … it was a historic, very important process," he said.

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

Erdogan has said that Turkey will discuss its participation in the coalition during this month’s U.N. General Assembly. The U.S. ally and member of the NATO military alliance has made commitments of only limited help in the fight against the Islamic State group, which has seized large parts of Syria and Iraq and rules by its harsh version of Islamic law.

The U.S. is looking for major participation from nations in the region in the campaign to destroy the Islamic State group. President Barack Obama has pledged that no American troops will be involved in combat missions against the group, and the U.S. expects nations in the region to provide those.

The Islamic State group released a new audio recording online late Sunday in which a spokesman urged Muslims worldwide to kill civilians of those nations that join the fight. A French citizen was kidnapped in Algeria by an al-Qaida splinter group that said it will kill him unless France ends its participation in airstrikes against the Islamic State group in Iraq, officials said.

Army Gen. Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, said Monday he remained hopeful that Turkey would participate in the coalition.

"We need Turkey, frankly," he said during a visit to Croatia, because of its military capability, regional influence and political gravitas in the Muslim world.

But Turkey may also have questions for the U.S., if the support that Washington gives to Kurds in Iraq is extended to the Kurds fighting in Syria. Iraqi Kurdish peshmerga fighters are already starting to get training by Iraq’s Western allies in fighting the Islamic State group.

"The U.S. says it will make sure that arms won’t go to the PKK, but this isn’t possible," said Hasan Koni, a professor of international law at Istanbul’s Kultur University. He added that the tensions have brought the peace process to its most difficult phase as Kurds question Turkey’s ambivalent stance in their fight in Syria and Iraq.

"The Kurds could say: what kind of a peace is this? We are being strung along," he said.

Turkish authorities may have concerns that Turkey’s Kurds, bolstered by Western arms and emboldened by battlefield success, could harden their demands on the government in Ankara.

Beyond the political questions, the conflict is adding to a huge burden for Turkey. On Monday, Deputy Prime Minister Numan Kurtulmus warned that the number of Syrians crossing the border could rise further to "a refugee wave that can be expressed by hundreds of thousands."

"This is not a natural disaster. … What we are faced with is a manmade disaster," Kurtulmus said of the surge of mostly women, children and the elderly that started late Thursday.

Suzan Fraser in Ankara, Turkey, Mohammed Rasool in Suruc, Turkey, and Bassem Mroue in Beirut and contributed to this report.