Intensified air strikes helped Kurdish militia push back Islamic State jihadists fighting for Kobane as pressure mounted Wednesday for more international action to save the key Syrian border town.

Across the frontier in Turkey, the government's lack of action against the jihadists was drawing a furious response, with at least 14 people killed in pro-Kurdish demonstrations in the southeast.

A new strike by the US-led coalition hit near Kobane early Wednesday after a flurry of raids the day before, an AFP reporter on the Turkish border said.

The strike sent a cloud of thick black smoke billowing from the eastern side of the town, where Kurdish militia were reported to have forced IS fighters out of several neighbourhoods in heavy overnight fighting.

The jihadists pierced Kobane's defences this week, sparking fierce street battles that continued on Wednesday with the sounds of heavy gunfire and mortar shells falling on the town.

A Kobane official, Idris Nahsen, said fighters from the Kurdish People's Protection Units (YPG) had managed to push IS militants out of key areas after "helpful" air strikes by the US-led coalition.

"The situation has changed since yesterday. YPG forces have pushed back ISIS forces," he told AFP, using another name for the extremist group.

The Syrian Observatory for Human Rights, a Britain-based monitoring group, also said IS fighters had withdrawn overnight from several areas and were no longer inside the western part of Kobane.

Observatory director Rami Abdel Rahman, whose group relies on a network of sources inside Syria, said the withdrawal came after coalition air strikes hit IS positions "causing casualties and damaging at least four of their vehicles."

But he said the jihadists had launched a new assault on Wednesday in the east of the town, also known as Ain al-Arab, following their pull-back.

"There are fierce clashes underway in the east of Ain al-Arab after the Islamic State launched an offensive to retake the areas it lost control of," Abdel Rahman said.

The Observatory said at least 32 IS fighters were killed in and around Kobane on Tuesday, including at least 20 in coalition air strikes.

It says about 400 people, more than half of them jihadists, have been killed in and around Kobane since IS began its assault in mid-September.

Washington and its allies have stepped up their air raids around Kobane in recent days, as the town became an important symbol of resistance to IS.

The group has seized control of large parts of Syria and Iraq, declaring an Islamic "caliphate" and committing widespread atrocities.

Kobane would be a major prize for the jihadists, giving them unbroken control of a long stretch of Syria's border with Turkey.

The Pentagon said coalition strikes near Kobane on Monday and Tuesday had damaged or destroyed several armed vehicles, anti-aircraft artillery, a tank and a jihadist "unit".

AFP correspondents reported hearing at least eight strikes around Kobane on Tuesday.

Amid warnings of Kobane's imminent fall, the UN envoy to Syria, Staffan de Mistura, joined calls for the international community to take urgent action.

"The world, all of us, will regret deeply if (IS) 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," he said.

"The international community needs to defend them. The international community cannot sustain another city falling under (IS)".

Washington launched its air campaign against IS in Iraq in August and last month expanded it to Syria with the participation of five Arab allies.

The Turkish parliament has voted to join the campaign but Ankara has yet to announce military action despite the advance of the jihadists on its doorstep.

Turkish President Recep Tayyip Erdogan warned on Tuesday that Kobane was "about to fall", saying a ground operation was needed to defeat the fighters.

"I am telling the West -- dropping bombs from the air will not provide a solution," he said.

Ankara has come under increasing pressure to act in Kobane but its response has been complicated by concerns over emboldening Kurdish separatists, who have waged a deadly insurgency in Turkey for the past three decades.

The Turkish army has deployed in the streets of several southeastern cities including the main Kurdish city of Diyarbakir, where intense rioting took place overnight.

Clashes have previously erupted in the border area close to Kobane, where some 200,000 mainly Kurdish refugees have fled the IS advance.

The United States and its allies have launched nearly 2,000 air raids against jihadists in both Iraq and Syria -- with Canada the latest to join the campaign after lawmakers on Tuesday approved a six-month mission.

In Iraq on Wednesday, a military helicopter crashed near Baiji, about 200 kilometres (120 miles) north of Baghdad, killing the crew, a senior officer and residents said.

An army colonel said the cause of the crash was not immediately clear but residents in Seiniye, where the helicopter went down, said it had been hit by jihadist fighters.