Undercover armed security guards begin random patrols of flights between Australia and Singapore on Tuesday, as part of a deal between the two nations to boost aviation security in southeast Asia.

Australia's Justice Minister Chris Ellison said the air route to and from Singapore is one of the busiest for Australia, with more than 12,000 flights a year by Qantas and Singapore Airlines.

Similar air security deals were also being negotiated with the United States and Canada, he said.

"It is vital in the current security environment that governments use all measures at their disposal to increase the security of the public and to maintain public confidence in aviation," Ellison said in a statement.

Australia started putting armed guards on random domestic flights two years ago, after the attacks on the United States on September 11, 2001, when hijacked airliners crashed in New York and Washington.

Ellison said the timing and nature of deployment of air security guards on both domestic and international flights would stay confidential.

The agreement, signed in Singapore on Monday, does not extend to airlines from other airlines flying between Singapore and Australia.

(Reuters)