A first group of Iraqi Kurdish peshmerga fighters entered the besieged Syrian town of Kobane to help push back Islamic State militants who have defied US air strikes and threatened to massacre its Kurdish defenders.
Kobane, on the border with Turkey, has been encircled by the Sunni Muslim insurgents for more than 40 days. Weeks of air strikes have failed to break their stranglehold, and Kurds are hoping the arrival of the peshmerga will turn the tide.
The siege of Kobane -- known in Arabic as Ayn al-Arab -- has become a test of the coalition's ability to stop Islamic State's advance, and Washington has welcomed the peshmerga's deployment. It has intensified its air strikes in the past two days ahead of their arrival.
A first contingent of about 10 peshmerga fighters arrived in Kobani from Turkey to prepare the way for a convoy equipped with heavy weapons, but gunfire and shelling by Islamic State fighters on the border area appeared to be causing delays.
"ISIL has intensified its attacks on the border gate after the news of the peshmerga's arrival ... and the clashes have been fierce," Idris Nassan, deputy foreign minister of Kobani district, told Reuters by telephone from Kobane.
The peshmerga fighters already in Kobane were trying to secure safe passage for the weapons convoy and the Turkish authorities, fearing a spillover onto Turkish soil, also wanted them to wait until the security situation was clearer, he said.
"With the ISIL shelling and the clashes, the whole process is taking time," Nassan said.
Hemin Hawrami, a senior official in the Kurdistan Democratic Party in Iraq, wrote on Twitter that the peshmerga already in Kobane were assessing where the heavy weapons would be deployed.
Around 100 peshmerga fighters arrived by plane in southeastern Turkey on Wednesday, joined later that night by a land convoy of vehicles carrying arms including a cannon and truck-mounted machine guns.
In a compound protected by Turkish security forces near the border town of Suruc, the fighters were donning combat fatigues and preparing their weapons, a Reuters correspondent said.
US forces stepped up air strikes on Islamic State positions in an apparent bid to help clear the way for the peshmerga. US Central Command said there had been 10 strikes near Kobane since Wednesday, hitting two small insurgent units and destroying seven fighting positions and five buildings.
Syria condemned Turkey for allowing foreign fighters and "terrorists" to enter Syria in a violation of its sovereignty. Its foreign ministry described the move as a "disgraceful act".
Turkey, which is a staunch backer of rebels fighting to oust Syrian President Bashar al-Assad, dismissed the comments.
"The Syrian regime has no legitimacy. Such statements from a regime that has lost its legitimacy are astonishing," a senior Turkish government official said.
Around 200 Free Syrian Army (FSA) fighters have also entered Kobane from Turkey to support the fight against Islamic State, according to rebel commander Abdul Jabbar al-Oqaidi and a second Turkish government official.
Nizar Al Khateeb, commander of an FSA unit that has been fighting alongside the Kurds in Kobane, said the FSA, peshmerga and Syrian Kurds would work from the same operations room and had no problem with the YPG, the main Syrian Kurdish armed group defending the town, leading the operation.
The FSA is a term covering dozens of armed groups fighting Assad but with little or no central command, and widely outgunned by Islamist insurgents elsewhere in the conflict.
Iraqi Kurdistan President Masoud Barzani said he was prepared to deploy more forces to Kobane if asked.
"Whenever the situation on the ground necessitates and more forces are requested from us and there is passage for them, we will send more forces to protect Kobane and defeat terrorists in Western Kurdistan," he said.
Islamic State has caused international alarm by capturing large expanses of Iraq and Syria, declaring an Islamic "caliphate" that extends across the borders between the two.
Its fighters have slaughtered or driven away Shi'ite Muslims, Christians and other communities who do not share their ultra-radical brand of Sunni Islam.
In Iraq, the bodies of 220 members of a Sunni tribe captured by Islamic State this week have been found in two locations, according to security officials and witnesses.
The Islamic State advance has deepened Syria's existing conflict. The United Nations said on Thursday the humanitarian crisis in the country was getting worse as all parties show "callous disregard" for millions of suffering civilians.
The United States and its allies in the coalition have made clear they do not plan to send troops to fight Islamic State in Syria or Iraq, but they need fighters on the ground to capitalize on their air strikes.
Syrian Kurds have called for the international community to provide them with heavier weapons and munitions and they have received an air drop from the United States.
But NATO member Turkey accuses Kurdish groups in Kobane of links to the militant PKK (Kurdistan Workers' Party), which has fought a three-decade insurgency against the Turkish state and is regarded as a terrorist group by Ankara, Washington and the European Union.
Ankara fears Syria's Kurds will exploit the chaos by following their brethren in Iraq and seeking to carve out an independent state in northern Syria, emboldening PKK militants in Turkey and derailing a fragile peace process.
That has enraged Turkey's own Kurdish minority, complicated efforts to provide aid, and meant the negotiations to enable the passage of the peshmerga were delicate and complex.
"If (Islamic State) defeats the Kurds in Kobane it will lead to a reaction amongst the Kurds around the world, including Turkey," said Fuad Hussein, chief of staff to Barzani.
"There is huge interaction: what happens here, what happens in Kobane, what happens in Turkey: it affects each other so we must manage it," he said.
Turkey's pro-Kurdish HDP party, which accuses the government of favoring Islamic State over the Kurds, called for marches on Saturday in solidarity with Kobane.
Around 40 people were killed in violence that swept the southeast earlier this month as Kurdish protesters expressed fury over Turkey's refusal to send its own troops across the border to defend the besieged town.
The peshmerga were given a heroes' welcome as their convoy of jeeps and flatbed trucks snaked its way for around 400 km (250 miles) through Turkey's mainly Kurdish southeast on Wednesday.