The fire forced the closure of all northbound lanes and one southbound lane of Lane Cove Road around lunchtime, and despite all lanes reopening by 5.30pm, traffic issues continued until after the evening peak hour rush.

Authorities advised motorists to allow extra travel time and drive to the conditions, with a lot of smoke in the area.

Buses also experienced delays up to 50 minutes, and some routes diverted from Lane Cove Road.

The bushfire was first reported shortly after 11am, a Fire and Rescue NSW spokeswoman said. The fire had jumped the road by the early afternoon, and it took a number of hours to bring it under control.

As of 4.30pm, the fire had been contained within control lines, and some backburning operations were under way with the National Parks and Wildlife Services in the south west corner of the park, bordered by Lane Cove Rd and Riverside Drive.

Water bombing was used to fight the fire, and helicopters were on the scene much of the afternoon providing aerial assistance, along with dozens of firefighting crews.

The spokeswoman said no injuries have been reported and no properties are under threat.