ARBIL, Iraq/MURSITPINAR, Turkey, Oct 28 (Reuters) - Iraqi peshmerga fighters headed for the Syrian town of Kobani on Tuesday to help fellow Kurds repel an Islamic State advance that has defied U.S.-led air strikes and become an important test of the coalition's ability to combat the Sunni insurgents.
Kobani, nestled on the border with Turkey, has been besieged by Islamic State for more than a month. Weeks of air strikes on the insurgents' positions and the deaths of hundreds of their fighters have failed to break the siege.
Islamic State has caused international alarm by capturing large expanses of Iraq and Syria, declaring an Islamic "caliphate" erasing borders between the two and slaughtering or driving away Shi'ite Muslims, Christians and other communities who do not share their ultra-radical brand of Sunni Islam.
The Islamic State (IS) has threatened to massacre Kobani's defenders in an assault which has sent almost 200,000 Syrian Kurds fleeing to Turkey, and triggered a call to arms from Kurds across the region.
Hemin Hawrami, a senior official in the Kurdistan Democratic Party in Iraq, wrote on his Twitter feed that peshmerga combatants were flying from Arbil airport in northern Iraq to Turkey, from where they would travel overland to Kobani.
Saleh Moslem, co-chair of the Syrian Kurdish Democratic Union Party (PYD), said later that around 150 peshmerga had entered Turkey from Iraq and were expected to reach the area of Kobani later on Tuesday night.
A Kurdish television channel showed footage of what it said was a convoy of peshmerga vehicles in northern Iraq loaded with weapons and on their way to the besieged town.
"We welcome the deployment of peshmerga fighters and weapons from the Kurdistan Region to Kobani, which began this evening," Brett McGurk, a deputy envoy tasked by U.S. President Barack Obama with building a coalition against IS, said on Twitter.
The Iraqi Kurdish region's parliament voted last week to deploy some peshmerga to Syria although a Kurdish government spokesman later said they would not engage in direct combat in Kobani but rather provide artillery support.
Kurdistan's Minister of Peshmerga, Mustafa Sayyid Qader, told local media on Tuesday that no limits had been set to how long the forces would remain in Kobani.
The fighting around Kobani has exacerbated the flow of refugees from Syria's 3 1/2-year civil war, with more than three million people already sheltering in neighboring countries including Jordan, Lebanon and Turkey.
Jordan's foreign minister warned on Tuesday the huge demand for housing, schools, jobs and health care generated by the refugees meant Syria's neighbors were reaching the limits of their ability to cope.
Turkish Prime Minister Ahmet Davutoglu said earlier that air strikes alone would not be enough to push back the insurgents and that only the peshmerga and moderate Syrian rebel forces could oust Islamic State from Kobani.
"Saving Kobani, retaking Kobani and some area around Kobani from ISIS, there's a need for a military operation," he said in an interview with the BBC broadcast on Tuesday. But he made clear neither Turkey nor Western allies would commit troops.
"If they (international coalition) don't want to send their ground troops, how can they expect Turkey to send Turkish ground troops with the same risks on our border?" Davutoglu said.
Turkish officials have rebuffed international criticism over their reluctance to do more to help Kobani's beleaguered Kurdish defenders, whom they accuse of being linked to the militant Kurdistan Workers' Party (PKK), which has fought a decades-long insurgency against the Turkish state.
That stance has enraged Turkey's own Kurdish minority - about a fifth of the population and half of all Kurds across the region. Kurds suspect Ankara would rather see Islamic State jihadists extend their territorial gains than allow Kurdish insurgents to consolidate local power.
Turkey has repeatedly called for a long-term strategic plan for Syria involving the removal of President Bashar al-Assad from power, fearing that Assad's forces or Kurdish militants will fill the void if Islamic State is neutralized.
Iran accused Turkey on Tuesday of prolonging the three-year armed conflict in Syria by insisting on Assad's overthrow and supporting "terrorist groups" in Syria.
After pressure from Western allies, Turkey last week agreed to let peshmerga forces from Iraq traverse its territory to reach Kobani as its preferred alternative to U.S. planes air-dropping weapons to Kurdish fighters in the town.
"The only way to help Kobani, since other countries don't want to use ground troops, is sending some peace-oriented or moderate troops to Kobani. What are they? Peshmerga ... and Free Syrian Army (Syrian opposition forces)," Davutoglu said.
Davutoglu renewed calls for the United States to train and arm fighters from the Free Syrian Army (FSA), a loose, disorganized coalition of groups who have been battling Assad and who have long been supported by Turkey.
Washington has committed to arming the Syrian opposition to fight Islamic State, but U.S. officials remain concerned about identifying effective, moderate groups in the increasingly sectarian Syrian conflagration. (Additional reporting by Stephen Brown in Berlin, Ece Toksabay in Istanbul, Jonny Hogg in Ankara; Writing by Nick Tattersall; Editing by Mark Heinrich)