City Ocean Safety officials yesterday posted warning signs at Waimea Bay and Waikiki following confirmed shark sightings in those areas.

Lifeguards saw a shark, 6 to 8 feet long, at Waimea Bay about 10:15 a.m. and posted warning signs, said city Emergency Services spokesman Bryan Cheplic. The signs were to remain posted overnight, he said.

Officials also posted signs in Waikiki in the Duke's Beach area after a lifeguard spotted a shark, 2 to 4 feet long. The signs were removed at 3:30 p.m.

A shark sighting Oct. 21 off Kailua Beach prompted officials to post signs for several hours.