A large tree from outside the rail corridor fell on overhead lines near Killara Station just before peak hour on Monday.

The disruption closed the line between Chatswood and Gordon, requiring replacement buses to service Roseville, Lindfield and Killara stations.

It is understood that the tree came down on the lines almost at the same time as a train passed through the area, however there was no incident.

At 7pm Sydney Trains had not yet been able to remove the tree from the lines but was confident of doing so before Tuesday morning.

Trains right through the northern suburbs have been delayed, however, and at 7pm there were flow-on delays to Western Line services through Parramatta and the Blue Mountains.

The Transport Management Centre said: "Anyone travelling from the city to Gordon, Pymble, Turramurra, Warrawee, Wahroonga or Waitara is advised to catch a train to Hornsby then another train to their destination.

"Central Coast & Newcastle Line trains are operating via Macquarie Park instead."

Separately, a multi-car crash at Edgecliff closed New South Head Road in the area, though the road re-opened at about 7pm.

"Traffic is very heavy and is queued back to William Street," the Centre said.

"Motorists already in the area should allow plenty of extra travel time and expect significant delays.