Beaches at the Australian city of Newcastle were closed for a seventh day on Friday after at least two large sharks were sighted in coastal waters.

A 5-meter (16-foot) great white shark estimated to weigh 1.7 metric tons (1.9 tons) had been spotted daily since last Saturday until Thursday off the coast of Newcastle, a city of 315,000 people 160 kilometers (100 miles) north of Sydney, Newcastle City Council said.

Photographs appeared in Australian media of a 3.5-meter (11-foot) shark mauling a dolphin on Thursday off Burwood Beach 200 meters (yards) from where divers were ignoring the beach closure by spearing fish.

A 3.5-meter shark was again spotted off the same beach on Friday morning, the council said in a statement. It was not clear what type of shark it was or whether it was the same shark as attacked the dolphin.

Lifeguards were working long shifts to warn beachgoers to stay out of the water.

Long-term employees of the council could not recall sharks closing city beaches for so long.

The beach closure comes during peak tourist season with schools closed for the summer vacation.

Danny Bucher, a Southern Cross University marine biologist, expected the great white shark would eventually leave Newcastle.

"As a general rule they're nomadic, but if there's a reliable supply of food, they'll hang around while that food lasts," Bucher said.