Four Westpac hostages safe

Four Westpac employees who survived the Lindt cafe siege that gripped Sydney overnight are safe.

Westpac CEO Gail Kelly said the 16-hour siege marked a sad day for Australia.

"My heart goes out to anyone touched by this tragedy," Ms Kelly said.

"However, it is with relief that we can confirm this morning that all four of our people - including two from one of our technology partners - are safe and accounted for following the incident.

"Our primary concern is the wellbeing of our people who were involved in this traumatic incident, along with their families," Ms Kelly said in a statement.

Westpac's Sydney headquarters in Martin Place is directly opposite the Lindt cafe.

Ms Kelly said the bank will not be providing any further comment.