The U.S.-led coalition stepped up airstrikes around the Syrian border town of Kobane on Tuesday after Turkey appealed for help, enabling Kurdish fighters to reverse the advance of Islamic State militants for the first time since the extremists launched their assault about three weeks ago.

The strikes followed the request by Turkey for intensified U.S. efforts to prevent the predominantly Kurdish town, known as Ayn al-Arab in Arabic, from falling to the Islamic State, Turkish officials said. Turkey has lined up tanks and troops within view of the Syrian Kurdish fighters defending Kobane but has not sought to intervene — for a tangle of reasons bound up with its complicated relationship with Kurds and its doubts about the goals of the international coalition fighting the extremists.

Turkey insisted, however, that it does not want the town to fall, and a senior official said Ankara asked the United States on Monday to escalate strikes.

“Turkey will not be content with the fall of Kobane into the hands of terrorist organizations,” Deputy Prime Minister Yalcin Akdogan said in a statement Tuesday.

“Our government and related institutions have underlined the necessity to intensify aerial bombings in a more active and effective way through contacts with U.S. officials until late into yesterday night,” the statement added.

The State Department declined to comment on the discussions, with spokeswoman Jen Psaki saying only that Secretary of State John F. Kerry spoke on the phone twice with Turkish Prime Minister Ahmet Davutoglu, on Monday night and, briefly, on Tuesday morning. The conversations were “broadly about the challenges we’re facing with ISIL and also Kobane,” she said, using an alternative acronym for the Islamic State.

Meanwhile, in Baghdad, officials said Wednesday that Islamic State militants downed an Iraqi military helicopter near the oil refinery town of Baiji, killing the two pilots on board.

A military aviation official told the Associated Press that the militants used a shoulder-fired missile to take down the helicopter. Baiji, some 130 miles north of Baghdad, is home to Iraq’s largest oil refinery. This is the second Iraqi military helicopter shot down over Baiji in a week.

Turkey has been widely criticized for its perceived inaction, but many Syrian Kurds also have accused the United States of neglecting their plight, contrasting the Islamic State’s unchecked advance on Kobane with the swift response to the group’s gains against Kurds in Iraq in the summer.

The U.S. Central Command on Tuesday reported five strikes around Kobane, doubling the number carried out since the Islamic State offensive against the town began. The strikes destroyed three Islamic State vehicles and an antiaircraft artillery piece, damaged a tank and took out a “unit,” a Central Command statement said.

The air attacks came just as the Islamic State launched a push into the center of the town, an advance that at first appeared to succeed, said Kurdish activist Mustafa Abdi, speaking from the adjoining Turkish town of Suruc. Islamic State fighters had reached the center of Kobane by mid-morning, he said, but one of the airstrikes hit a convoy of re­inforcements. It was forced to turn back, and the advancing fighters lost momentum.

By nightfall, a Kurdish force known as the People’s Protection Units had pushed the militants almost back to the position from which they had begun their attack. “Today is the first day the strikes were effective,” Abdi said. “These airstrikes are neutralizing their heavy weapons.”

Here's a closer look at the countries fighting the Islamic State and what they have to gain by banding together. (Davin Coburn/The Washington Post)

He said that more than 20 Kurdish fighters were killed and that the bodies of at least 50 militants were strewn in the streets. The claims could not be independently verified.

The Islamic State fighters responded to their setback with a barrage of artillery fire against the town, which Kurdish activists say has been almost entirely emptied of civilians and is being defended by about 3,000 fighters confronting up to 10,000 militants.

Kobane is still at risk, said Ibrahim Kader, another activist, urging continued strikes. “We do not have enough ammunition to last for much longer,” he said.

Kobane has little strategic value, and the Islamic State already controls several towns along the Turkish border. But the militant assault coincided with the extension of the U.S.-led air campaign from Iraq to Syria last month, putting the spotlight on the Islamic State’s advances in Syria — and on Turkey’s absence from the coalition formed to fight the group.

After warning that Kobane was “about to fall,” Turkish President Recep Tayyip Erdogan spelled out his nation’s conditions for joining the coalition, including the creation of a no-fly zone over portions of northern Syria — which could embroil the coalition in a fight with Syrian President Bashar al-Assad, as well.

“I am telling the West — dropping bombs from the air will not provide a solution,” Erdogan told a crowd of Syrians in the southern Turkish city of Gaziantep, whose population has swelled because of the influx of more than 1.5 million refugees into the country. More than 160,000 have arrived since the battle for Kobane began.

“The terror will not be over . . . unless there is cooperation for a ground operation,” Erdogan said Tuesday.

He also said it was crucial for “the moderate opposition in Syria and Iraq to be trained and equipped.” The Obama administration also has proposed similar measures but remains slow to act because of worries of al-Qaeda­inspired groups among the rebel ranks.

Underscoring the domestic ramifications of Turkey’s inaction, Kurds have been staging protests across the country and in some European cities demanding stronger measures to protect Kobane. In Varto, a town in eastern Turkey, a demonstrator was killed during clashes with security forces, news reports said.

Murphy reported from Washington. Carol Morello in Washington contributed to this report.