Former U.S. President Barack Obama visits Government House at Mount Eden, Auckland, New Zealand March 22, 2018. Reuters/Simon Watts/for Dept of Internal Affairs/Handout

Former US president Barack Obama arrived in the Harbour City on Friday as he is due to speak at the Art Gallery of New South Wales. Australian Prime Minister Malcolm Turnbull also tweeted a photo of him with Obama.

A motorcade of security and police greeted Obama on the tarmac after his private jet landed in Sydney. There has been heavy police presence around the CBD.

The former POTUS posed for photos at the Sydney Opera House and waved to a crowd. He later took a walk through the private gardens at Government House.

Obama is back in Australia to attend an event at the Gallery of New South Wales. Aside from being a guest of honour at the event, the 24-hour trip also includes a meeting with the Australian prime minister.

Turnbull was quick to post a welcome message. In his Twitter post, he called Obama “President,” something that his followers did not fail to notice.

While some pointed out that he is no longer POTUS, others argued that all US presidents retain their title and that Obama will always be referred to as "Mr President" or "the President.”

“News reports will often say former for clarity's sake, but referring to him as President Obama is correct,” one Twitter user wrote.

Turnbull said on Thursday that he will be having a chat with Obama, adding that he looks forward to catching up with the former POTUS.

The 44th president’s visit comes after a three-day stay in New Zealand, where he met with New Zealand Prime Minister Jacinda Ardern and former leader John Key. Obama offered some parenting tips to Ardern, who is expecting her first child in June. When she asked him how he dealt with the guilt of being a parent and a world leader at the same time, he advised her to “do the best you can,” ​The Daily Mail reports. On Thursday, actor Sam Neill hosted a discussion with Obama in Auckland.

As for Obama’s speaking engagement in Australia, there are reportedly no tickets available for purchase as the guest list is "invitation only.” Aside from Australia and New Zealand, Singapore and Japan are also listed on Obama’s week-long tour.