South Africa's President Jacob Zuma (L) arrives at Brisbane Airport to attend the G20 Summit in Brisbane, Australia, Nov. 12, 2014. (Xinhua)

BRISBANE, Australia, Nov. 13 -- Leaders and delegations from Saudi Arabia, Argentina, Brazil and Turkey are all scheduled to arrive in Brisbane on Thursday for the G20 leader's summit.

International Monetary Fund Managing Director Christine Lagarde is also due to arrive on Thursday at the city which is undertaking one of Australia's largest ever security operations.

South African President Jacob Zuma was the first world leader to arrive in Brisbane when his plane landed on Wednesday.

Queensland Premier Campbell Newman was there to greet the South African president who was then swept away in a black Mercedes surrounded by police cars, vans and motorcycles through heavily barricaded streets.

The 100 million Australian dollar (87 million U.S. dollar) G20 security operation is focusing on the Brisbane Convention and Exhibition Center, where the summit is being staged, hotels where the world leaders will stay and surrounding roads.

Many road closures have been set up and the down town area of Brisbane has been relatively deserted.

The most visible security activity so far has been linked to the arrival of U.S. President Barack Obama, who is expected early on Saturday.

Three U.S. helicopters practiced military drills on Wednesday, and the campus at the University of Queensland has been made a special security zone because Obama is scheduled to deliver a speech to students there on Saturday.

According to The Australian newspaper on Thursday, U.S. officials requested that a roundabout outside the university be demolished so Obama's motorcade would not need to slow down.

But the request was turned down by Queensland authorities, which would not comment on specific security measures.

In the lead-up to the G20 event, police have been working with more than 20 protest groups, who are planning peaceful demonstrations, mostly on Saturday when the summit officially begins.

Police said there was a chance that some peaceful protests could be disrupted by radical demonstrators, which have caused violence and property damage at previous G20 summits.

More than 6,000 police and 900 soldiers have been deployed around Brisbane before the summit.