(CNN) -- It's too soon to say what steps the United States will take against ISIS in Syria, President Barack Obama said Thursday.
"I don't want to put the cart before the horse," Obama said. "We don't have a strategy yet."
Obama said he's asked U.S. military leaders to prepare "a range of options" about what the United States could do to go after ISIS in Syria, which he said has become "a safe haven" for the Islamist group.
In Syria, he said, it's a political issue as well as a military one -- and something regional leaders need to address.
Obama said he was sending U.S. Secretary of State John Kerry to the region to work on building a coalition needed to face the threat of ISIS militants.
"This should be a wake-up call to Sunni, to Shia, to everybody, that a group like ISIS is beyond the pale, that they have no vision or ideology beyond violence and chaos and the slaughter of innocent people. And as a consequence, we've got to all join together," Obama said, "even if we have differences on a range of political issues, to make sure that they're all rooted out."
U.S. airstrikes in Iraq are working, Obama said.
"The terrorists of (ISIS) are losing arms and equipment," he said, and Iraqi and Kurdish forces are making inroads.
But "the idea that the United States or any outside power would perpetually defeat ISIS ... is unrealistic," Obama said, insisting that a strong, trusted Iraqi government is critical to ousting the Islamist terror group permanently.
ISIS said Thursday that it has executed at least 250 Syrian soldiers at an air base in the northeastern city of Raqqa.
The group said on one of its official websites that it killed the soldiers Wednesday. It also claimed to have killed 600 government soldiers in the fight for the al Tabqa air base since August 19.
The Syrian Observatory for Human Rights, meanwhile, reported that 200 Syrian soldiers and 346 ISIS fighters died in the fight for the air base. Hundreds more were wounded, the London-based activist group said.
ISIS claims that a video it posted online Thursday shows Syrian soldiers being paraded through the desert in their underwear. Another video posted by Syrian activists purportedly shows bodies lined up on the ground.
Later, ISIS posted a video that it says shows captured Peshmerga soldiers wearing orange clothing similar to that worn by by American journalists James Foley and Steven Sotloff in other videos posted by the militant group.
Three masked men appear to decapitate an orange-clad man in front of a mosque in Mosul.
In the video, titled "A message with blood to the leaders of the America Kurdish alliance," ISIS demands that the Kurdish government withdraw its forces from areas where it is battling the group.
CNN could not independently confirm the claims or the authenticity of the videos.
The videos come amid reports of fresh fighting between ISIS and Kurdish forces near Iraq's Mosul Dam and the burning of oil wells near the strategic town of Zummar, Iraq.
The Peshmerga are battling the militants near the town, important because of its location near a main road connecting Mosul to the Syrian border, as well as near the Mosul Dam and the strategic Ayn Zala oilfields, which ISIS forces seized from the Kurds this month, said Faud Hussein, chief of staff for Kurdish regional President Masoud Barzani.
Torching the oil wells is an apparent effort by ISIS fighters to cover their tracks as Peshmerga forces press toward ISIS positions, Hussein said.
The extent of the damage to the oil fields wasn't immediately known.
At least 50 ISIS militants were killed in fighting near the Mosul Dam on Thursday, said Hemin Hawrami, head of the Foreign Relations Office of the Kurdistan Democratic Party. Kurdish forces also destroyed several ISIS vehicles, he said.
One Peshmerga fighter died and five were wounded in the fighting, Hawrami said.
The fighting comes nearly two weeks after thousands of Peshmerga and Iraqi commandos ousted ISIS forces for control of the dam, a crucial facility that provides electricity for millions of people in Iraq.
Kurdish officials have credited U.S. airstrikes against ISIS -- which calls itself the "Islamic State" -- with helping Peshmerga forces push back against ISIS forces, whose breathtaking gains and brutal tactics captured the attention of world leaders.
Meanwhile, U.S. President Barack Obama is considering airstrikes and humanitarian airdrops to help save thousands of Iraq's Shiite Turkmen, who officials said face potential slaughter by ISIS.
ISIS fighters have besieged the town of Amerli, about 140 miles (225 kilometers) southeast of Mosul, since the Sunni extremists swept into Iraq from Syria in mid-June. The town's fewer than 20,000 residents -- half of them women and children, according to the United Nations -- are without power.
"Residents are enduring harsh living conditions with severe food and water shortages, and a complete absence of medical services -- and there are fears of a possible imminent massacre," U.N. High Commissioner for Human Rights Navi Pillay said this week.
Their situation echoes the ordeal of Iraq's ethnic Yazidis, whose plight after they were forced to flee into the mountains to escape ISIS militants triggered U.S. aid drops and the first U.S. airstrikes against ISIS.
Similar to the chaotic scenes that played out in the Sinjar Mountains, Iraqi military helicopters have been carrying out food drops and picking up Turkmen desperate to get out.
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Surrounded on four sides, the 17,400 residents have had to defend themselves with only the help of local police, Masrwr Aswad of Iraq's Human Rights Commission has said.
ISIS has vowed to push the Shiite Turkmen out, calling them heretics.
Turkmen are descendants of Turkic-speaking, traditionally nomadic people who share cultural ties with Turkey. There are Sunni and Shiite Turkmen in Iraq, and they account for up to 3% of Iraq's population.
On Wednesday, U.N. human rights investigators accused ISIS and Syrian government forces of committing war crimes and atrocities in their brutal fight in Syria.
The U.N. report said public executions, torture and mock crucifixions have become regular fixtures in ISIS-controlled areas of Syria. It also said that the extremist group is forcing children to fight.
"Among the most disturbing findings in this report are accounts of large training camps, where children, mostly boys, from the age of 14 are recruited and trained to fight in the ranks of ISIS along with adults," said Paulo Pinheiro, the chairman of the U.N. commission of inquiry on Syria.
The report also accuses the regime of Syrian President Bashar al-Assad of repeatedly using chemical weapons against civilians.
The U.N. investigators said the Syrian government dropped what was thought to be chlorine gas on civilian areas on eight occasions in April.
The government forces are believed to have made particular use of barrel bombs dropped by helicopters to unleash the gas, said Vitit Muntarbhorn, a commissioner with the inquiry.
Chelsea J. Carter and Michael Pearson reported and wrote from Atlanta. CNN's Catherine E. Shoichet, Greg Botelho, Barbara Starr, Anna Coren, Hala Gorani and Jethro Mullen contributed to this report.