Northern Beaches Council announced the closure of the two popular beaches, saying the NSW Government Shark Smart app had reported a sighting of a “tagged shark in the vicinity” of the beaches.

This marks the fourth beach to be closed in the area, with Dee Why Beach and Long Reef Beach closed over the weekend after a fatal shark attack.

On Saturday, 57-year-old surfer Mercury Psillakis was attacked and killed by a large shark off Long Reef while surfing.

Psillakis was taken by a shark described by witnesses as being around five metres in length.

Fellow surfers say he spotted the predator  and began warning those around him.

In addition to the beach closures, a planned trial to take down shark nets from Sydney beaches was paused yesterday.

“We need to understand what happened and how it happened,” Premier Chris Minns told Sky News, after describing the attack as an “awful tragedy”.

“I think it’s also worth reporting that Dee Why is a netted beach and was not going to be part of the trial, so I need to understand whether the shark got inside the nets or how the system’s operating, before we make big moves.”