Islamic State in Iraq and Syria fighters were poised to capture a strategic Syrian town on the Turkish border, Turkey's president warned Tuesday, even as Kurdish forces battled to expel the extremists from their footholds on the outskirts.

The outgunned Kurdish fighters struggling to defend Kobani got a small boost from a series of U.S.-led airstrikes against the militants that sent huge columns of black smoke into the sky. Limited coalition strikes have done little to blunt ISIS's three-week offensive, and its fighters have relentlessly shelled the town in preparation for a final assault.

Warning that the aerial campaign alone was not enough to halt ISIS's advance, Turkish President Recep Tayyip Erdogan called for greater co-operation with the Syrian opposition, which is fighting both the extremists and forces loyal to Syrian President Bashar al-Assad.

"Kobani is about to fall," Erdogan told Syrian refugees in the Turkish town of Gaziantep, near the border. "We asked for three things: One, for a no-fly zone to be created; Two, for a secure zone parallel to the region to be declared; and for the moderate opposition in Syria and Iraq to be trained and equipped."

'Kobani is about to fall.' - Turkish President Recep Tayyip Erdogan

Erdogan's comments did not signal a shift in Turkey's position: He has said repeatedly that Ankara wants to see a more comprehensive strategy for Syria before it commits to military involvement in the U.S.-led coalition.

Turkish tanks and other ground forces have been stationed along the border within a few hundred yards of the fighting in Kobani, also known as Ayn Arab, but have not intervened. And while Turkey said just days ago that it wouldn't let Kobani fall, there's no indication the government is prepared to make a major move to save it.

More than 400 killed

Since mid-September, the militant onslaught has forced some 200,000 people to flee Kobani and surrounding villages, and activists say more than 400 people have been killed in the fighting. It has also brought the violence of Syria's civil war to Turkey's doorstep.

Capturing Kobani would give ISIS, which already rules a huge stretch of territory spanning the Syria-Iraq border, a direct link between its positions in the Syrian province of Aleppo and its stronghold of Raqqa, to the east. It would also give the group full control of a large stretch of the Turkish-Syrian border.

Syrian Kurds scoffed at the rhetoric coming out of Ankara. They say that not only are the Turks not helping, that they are actively hindering the defence of Kobani by preventing Kurdish militiamen in Turkey from crossing the border into the town to help in the fight.

"We are besieged by Turkey, it is not something new," said Ismet Sheikh Hassan, the Kurdish defence chief for the Kobani region.

Relations between Turkey and Syria's Kurds have long been strained, in large part because Ankara believes the Kurdish Democratic Union, or PYD the leading Syrian Kurdish political party is affiliated with the Kurdish PKK movement that has waged a long and bloody insurgency in southeast Turkey.

In towns across Turkey, Kurdish protesters clashed with police Tuesday, while Kurdish demonstrators forced their way into the European Parliament in Brussels part of Europe-wide demonstrations demanding more help for the besieged Kurdish militiamen struggling to defend Kobani. Turkish news agencies say least 14 people have died and scores were injured in clashes between Turkish police and Kurdish protesters.

'Airstrikes should be intensified'

Despite Erdogan's dire assessment of the battle for Kobani, the front lines were largely stable despite heavy clashes Tuesday.

Kurdish forces managed to push back ISIS militants from some neighbourhoods on the eastern edges of town, hours after the extremists stormed into the areas, according to the Britain-based Syrian Observatory for Human Rights. Still, two black jihadi flags fluttered from a building and a small hill on the eastern outskirts.

Fighting also raged at the southwestern entrance to town, where the militants have seized control of a few buildings, including a hospital, said Observatory director Rami Abdurrahman.

From the Turkish side of the border, plumes of smoke from ISIS shelling could be seen rising above the rooftops Tuesday, while long bursts of heavy gunfire frequently erupted followed by brief lulls.

The beleaguered Kurdish militiamen defending Kobani received some support overnight and Tuesday from the American-led coalition, which carried out six airstrikes against ISIS militants around the town, destroying four armed vehicles, damaging a tank and killing fighters, the U.S. military said.

An Associated Press journalist on the Turkish side of the border heard the roar of planes early Tuesday followed by massive explosions and large plumes of smoke billowing just west of Kobani.

The U.S.-led coalition has conducted similar airstrikes over the past two weeks near Kobani in a bid to help Kurdish forces defend the town. But the number has been limited, and Kurds have appealed for more help in the fight.

"The airstrikes should be intensified," said Idriss Nassan, deputy head of Kobani's foreign relations committee. "There should be strikes at night and during the day and weapons should be given to People's Protection Units (Kurdish militia) that could be considered part of the international coalition to fight terrorism."

Syria's Kurds have struggled to gain the sort of Western backing that their brethren in Iraq enjoy, and the aerial campaign around Kobani has been far more limited than the airstrikes against ISIS fighters attacking Iraqi Kurdish areas. The U.S. and its allies also have not agreed to arm Syrian Kurds like they have Iraqi Kurds.

The new UN envoy to Syria, Staffan de Mistura, called for an urgent international response to ISIS's assault on Kobani, saying the global community can't sustain another city falling to the extremist group.

"The world, all of us, will regret deeply if ISIS is able to take over a city which has defended itself with courage but is close to not being able to do so. We need to act now," Mistura said.

In Washington, State Department spokeswoman Jen Psaki said that U.S. Secretary of State John Kerry has spoken with Turkey Prime Minister Ahmet Davutoglu twice since Monday to discuss the situation in Kobani and Turkey's broader role in the coalition.

The United States and five Arab allies launched an aerial campaign against the Islamic State in Syria on Sept. 23 with the aim of rolling back and ultimately crushing the extremist group. The U.S. has been bombing ISIS targets in neighbouring Iraq since August.