Iraqi Kurdish Peshmerga forces have crossed from Turkey into Syria to join Syrian Kurds in the town of Kobani to fight against Islamic State (IS) militants.
The Peshmerga fighters -- who total some 150 soldiers -- came in small groups over the border overnight on October 31 with trucks carrying their heavy weapons.
Syrian Kurdish forces have held off IS fighters for several weeks and currently control about half of the town.
Tens of thousands of Kobani residents and other displaced persons who had earlier fled IS forces have sought refuge in Turkey.
The Peshmerga forces were cheered wildly by Kurds standing along the road as they approached the Syrian border, with many of the fighters raising their guns above their heads and chanting "Kobani, Kobani!"
The Britain-based Syrian Observatory for Human Rights said the Peshmerga entered through the western sector of the town, which was predominantly inhabited by Kurds before people fled.
The organization added that the arrival of the Iraqi Kurdish troops was accompanied by three air strikes by the U.S.-led international coalition on IS positions near Kobani.
The IS has been trying since mid-September to take the city, and has captured several Kurdish villages nearby.
But the air strikes begun last month have helped to keep the IS fighters from taking control of the important city.
Earlier on October 31, Turkish President Recep Tayyip Erdogan criticized the U.S.-led coalition for focusing too much on Kobani at the expense of other towns occupied by the IS.
Speaking in Paris after meetings with President Francois Hollande, Erdogan said that there is "almost no one left" in Kobani and he asked, "why bombard continuously this town."
Erdogan said there are other towns in Syria in need of help from air strikes by the coalition, citing Idlib.
Turkey has come under international criticism for not doing more to help Kobani, which is being defended by Syrian Kurds who have been trying to hold off an advance by the militants for weeks.
In Damascus, Ankara's decision to allow the Peshmerga to transit Turkey was harshly criticized as a "flagrant violation of Syrian sovereignty."
Meanwhile, a UN report said that the Islamic State group was recruiting foreign fighters on an "unprecedented scale."
The latest U.S. figures show that some 1,000 foreign fighters are joining IS each month.