Prime Minister Lee Hsien Loong starts a four-day official visit to Sydney today at the invitation of Australian Prime Minister Malcolm Turnbull.

PM Lee will take part in two events - the third Singapore-Australia Leaders' Summit, an annual bilateral meeting, and the Asean-Australia Special Summit, said a Ministry of Foreign Affairs statement.

Leaders attending both events are expected to discuss issues of common interest, such as regional security and the progress of the Regional Comprehensive Economic Partnership (RCEP).

The RCEP is a multilateral free trade pact whose members are China, the Asean countries, Australia, New Zealand, India, Japan and South Korea.

PM Lee will also have meetings with the Chief Commissioner of the Greater Sydney Commission Lucy Turnbull and New South Wales Premier Gladys Berejiklian.

A reception will be held for him to meet Singaporeans living in Australia.

As Singapore is the current Asean chair, PM Lee will co-chair the Asean-Australia Special Summit with Mr Turnbull.

On the summit's sidelines is a Small and Medium Enterprise Conference, at which he will give the opening speech. His wife Ho Ching, who is Temasek Holdings' chief executive, will do likewise at a Women in Business breakfast.

PM Lee will also witness the signing of the Asean-Australia Memorandum of Understanding on Cooperation to Combat International Terrorism. It will take place at a counter-terrorism conference, at which senior officials from Australia and Asean will also discuss improving cooperation to combat violent extremism.

Accompanying PM Lee are Foreign Minister Vivian Balakrishnan, Minister for Trade and Industry (Industry) S. Iswaran, and Social and Family Development Minister and Second Minister for National Development Desmond Lee, as well as senior government officials.