Attacking Islamic State jihadists met firm Kurdish resistance in the Syrian battleground town of Kobane, as neighbouring Turkey has heeded pressure to intervene and handed the US access to its air bases.
In Iraq however, Islamic State (IS) fighters have government forces under strong pressure, and a roadside bomb killed the police chief in Anbar province between Baghdad and the Syrian border.
Farther north, around Iraq's key oil refinery town of Baiji, the army and Sunni Arab tribal allies came under fresh IS attack, prompting a first resupply operation by coalition aircraft.
In Kobane, on Syria's border with Turkey, a pall of black smoke hung over the strategic town as the Syrian Observatory for Human Rights reported heavy jihadist losses.
IS poured in reinforcements and fired at least 11 rocket-propelled grenades into the town centre, said the Britain-based monitoring group.
The Kurds managed to advance 50 metres towards their headquarters, two days after the jihadists captured it, but failed to deliver a knockout blow.
"They (IS) are sending fighters without much combat experience," Observatory director Rami Abdel Rahman said.
Since proclaiming a "caliphate" straddling parts of Iraq and Syria in June, the militants have seized swathes of territory and earned worldwide infamy for atrocities - often videotaped and posted on the Internet.
Turkey, which has so far been reluctant to get involved in the fighting, has faced international pressure to step in to defend Kobane.
A senior US defence official said it has now granted the United States access to its air bases for the campaign, including a key installation near the Syrian border.
"Details of usage are still being worked out," the official told AFP.
In southern Turkey, US crews have long operated out of Incirlik Air Base and about 1,500 air force personnel are stationed there. US aircraft bombing IS militants are reportedly flying out of air bases in the United Arab Emirates, Kuwait and Qatar.
In a telephone call with Turkish Defence Minister Ismet Yilmaz, Pentagon chief Chuck Hagel thanked Turkey for its "willingness to contribute to coalition efforts, to include hosting and conducting training for Syrian opposition members," his spokesman said.
