Fierce U.S. airstrikes killed “several hundred” Islamic State fighters in and around the besieged Syrian city of Kobani, helping to swing some of the momentum back to the ethnic Kurds who have been battling the militants for months.

With warplanes active above, fighting on the streets, where Islamic State and Kurdish fighters have battled block by block for control of the city on the Turkish border, was quiet. Fox News correspondents stationed just across the border in Turkey, in view of the city, saw very little daylight fighting early Thursday, and sources inside Kobani said the terrorists have been beaten back by the huge U.S. coalition air barrage of the last two days.

“We have seized back quite some territory yesterday,” a Kurdish commander who gave her name as Dicle told Reuters early on Thursday.

Other sources fear the Islamic State fighters could be waiting out the airstrikes and preparing their next ground offensive.

Syrian Observatory for Human Rights estimates there have been 650 casualties from the month-long fight, including civilians driven to Kobani from smaller Kurdish villages in the region overrun by Islamic State. Observatory director Rami Abdul Rahman told AFP that Islamic State has lost 374 militants, while 268 people have been killed fighting on the Kurdish side. The agency also said Kurdish units had retaken several neighborhoods in Kobani, cutting Islamic State’s hold from half of the town to about 30 percent.

On Tuesday and Wednesday, U.S. warplanes unleashed a ferocious blitz of 39 strikes in 48 hours, killing “several hundred” jihadis and giving Kurdish fighters cover for an effective counterattack, the Pentagon said.

The air campaign also pinned down Islamic State fighters coming to the aid of those holding thee city under siege and disrupted supply lines.

The Syrian Observatory for Human Rights said Kurdish units had retaken several neighborhoods in Kobani, cutting ISIS’ control from 50 percent of the town to about 30 percent.

The Kurdish fighters have held off the militant marauders for more than a month, hanging on to their territory against long odds.

“People underestimate the power of determination,” said Farhad Shami, a Kurdish activist in Kobani. “The Kurds have a cause and are prepared to die fighting for it.”

Islamic State militants launched their offensive on Kobani in mid-September, capturing several nearby Kurdish villages and steadily strengthening their control around the town. The fighting forced at least 200,000 Kurds to flee into Turkey.

The town's population of 60,000 swelled to 400,000 in recent months as refugees - mainly Turkmen and Kurds - poured in to escape fighting elsewhere. Refugees who have fled to Kobani have recounted seeing their villages burned and their neighbors beheaded. Polat Tan, a senior commander with the Kurdish militia in Syria, which is defending Kobani, told last month that time is running out.

“We will do everything to resist these advances,” he said. “We will fight till every last drop of blood, but if help does not arrive soon, disaster is at hand.”

Fox News' Greg Palkot contributed to this report