Police in the state of New South Wales (NSW) said on Monday morning that authorities have resumed searching for the 11-year-old boy in waters off the state's Central Coast 60 km north of Sydney, reports Xinhua news agency.

Emergency services were alerted after witnesses reported that a child had been swept out to sea at about 5:15 p.m. local time on Sunday.

NSW Police said in a statement that a 43-year-old man was crossing The Entrance Channel, a 450-meter stretch of water between two headlands, with his four children when the eldest was swept into the ocean by the current.

"While two bystanders looked after the other three children, the man tried to reach the boy but was unsuccessful," police said.

The incident triggered a major search operation by land, sea and air, which continued until dark when it was suspended.

The search resumed at 8 a.m. local time on Monday.