"New fighting in northern Syria has seen 23,135 refugees fleeing across the border into Turkey's Sanliurfa province," during that period, spokesman William Spindler said, citing figures given by Turkish authorities on Tuesday.
"Some 70 percent are women and children," he said.
"Most of the new arrivals are Syrians escaping fighting by rival military forces in and around the key border town of Tal Abyad, which was controlled by militants and faces Akcakale across the border," he said.
"But they also include so far 2,183 Iraqis from the cities of Mosul, Ramadi and Fallujah," he added.
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He said UNHCR had provided 27,000 items of children's clothing, 33,000 blankets and 8,000 mattresses after being asked for assistance by Turkey's emergency relief agency.
Kurdish militia, backed by Syrian rebel forces, seized full control of Tal Abyad from the Islamic State group early on Tuesday, according to the Britain-based Syrian Observatory for Human Rights group.
The town's fall is a heavy blow to IS, which had used the adjacent border crossing with Turkey to bring in fighters and ammunition, and smuggle out black market oil, analysts say.