Police last month received reports a 14-year-old girl had been sexually assaulted by a man she knew.

He had communicated with the teenager through various social media platforms, police said, and after arranging to meet the girl he sexually assaulted her at a home in Sydney's north-west.

The State Crime Command's child abuse and sex crimes squad began investigating the incident and extensive inquiries led them to Tumut on Monday afternoon.

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The 21-year-old man was arrested in Tumut just after 2.30pm, and he was later charged with three counts of having sexual intercourse with a child between 14 and 16 years.

He was refused bail and is due to appear at Wagga Local Court today.

Anyone with concerns or information about suspected child abuse or exploitation should call Crime Stoppers on 1800 333 000.