Islamic State fighters launched a renewed assault on the Syrian city of Kobane tonight.
It came as at least 21 people were killed in riots in neighbouring Turkey where Kurds rose up against the government for doing nothing to protect their kin.
Heavily outgunned defenders said so called Islamic State militants had pushed into two districts of the mainly Kurdish border city tonight, despite US led airstrikes.
Earlier, the Pentagon acknowledged that US strikes would probably not be enough to safeguard the town.
In Turkey, street battles raged between Kurdish protesters and police across the mainly Kurdish southeast, in Istanbul and in Ankara.
The fallout from war in Syria and Iraq is threatening to unravel the NATO member's own delicate Kurdish peace process.
The street violence was the worst Turkey has seen in years.
Washington said its war planes, along with those of coalition ally the United Arab Emirates, had struck nine targets in Syria, including six near Kobane that hit Islamic State artillery and armoured vehicles.
It also struck Islamic State positions in Iraq five times.
Nevertheless, Kobane remained under intense bombardment from Islamic State emplacements, within sight of Turkish tanks at the nearby frontier that have so far done nothing to help.
"Tonight, (Islamic State) has entered two districts with heavy weapons including tanks. Civilians may have died because there are very intense clashes," Asya Abdullah, co-chair of the Democratic Union Party (PYD), the main Kurdish group defending the area, told Reuters news agency from inside the town.
US officials were quoted voicing impatience with the Turks for refusing to join the coalition against Islamic State fighters who have seized wide areas of Syria and Iraq.
Turkey says it could join only if Washington agrees to use force against Syrian President Bashar al-Assad and the Sunni Muslim jihadists fighting him in a three-year-old civil war.
Turkey's own Kurds, who make up the majority in the southeast of the country, say President Tayyip Erdogan is stalling while their brethren are killed in Kobani.
Police fired tear gas and water cannon to disperse demonstrators who burned cars and tyres.
Authorities imposed curfews in at least five provinces, the first time such measures have been used widely since the early 1990s.
Turkish Prime Minister Ahmet Davutoglu told reporters in Ankara that 19 people were killed and 145 wounded in riots across Turkey, vowing that Turkey's own peace process with Kurdish separatists would not be wrecked by "vandalism".
Dogan news agency later said the death toll had climbed to 21.
At least 10 people died in clashes in Diyarbakir, the largest Kurdish city in Turkey's southeast.
An all-day curfew there from last night was extended for another day today.
Pockets of protesters defying the curfew clashed with security forces there today.
Others died in clashes between protesters and police in the eastern provinces of Mus, Siirt and Batman.
Thirty people were wounded in Istanbul, including eight police officers.
Disturbances spread to other countries with Kurdish and Turkish populations.
Police in Germany said 14 people were hurt in clashes there between Kurds and radical Islamists.
The unrest in Turkey, which has NATO's second largest armed forces, exposes the difficulty Washington has faced in building a coalition to fight Islamic State in Syria and Iraq, two countries with complex, multi-sided civil wars in which every country in the region has a stake.
Australia conducts first air strikes in Iraq
Meanwhile, a Super Hornet fighter jet has carried out Australia's first bombing raid in the fight against the Islamist State group in Iraq, the defence ministry said.
"Two bombs were dropped from an F/A-18F Super Hornet on to an ISIL facility," the ministry said.
"All aircraft exited the target area safely and returned to base," it said.
