The bushfire threatening homes in south-western Sydney is worsening, with authorities issuing an emergency warning for some suburbs, telling residents it is "too late to leave" and advising them to seek shelter.

The fire is travelling in a north-easterly direction towards Georges River.

At 2.30pm on Sunday, residents in Voyager Point, Pleasure Point, Sandy Point and Illawong, as well as residents east of Alfords Point Rd in Menai and Bangor, were advised not to leave their properties and to protect themselves in expectation of an ember attack from the out-of-control fire.

In addition, residents west of Alfords Point Rd in Alfords Point and Barden Ridge were advised to shelter in place as the bush fire approached.