South Korea's defence ministry said Monday it has ordered its staff to install a smartphone application that restricts key functions like the camera in an attempt to prevent military leaks.

The ministry said that, from Monday, its 1,500 staff are no longer allowed to bring smartphones into their offices without installing the app, called "Mobile Management Device".

The order caused a long queue at the gates of the ministry on Monday because some 20 percent of the staff had failed to install the app, officials said.

The ministry declined to confirm a report by Yonhap news agency that some staff had refused to install the app due to concerns about privacy.

Ministry spokesman Kim Min-Seok told reporters that the app, which restricts the use of cameras and audio recording, prevents leaks through smartphones and stops outsiders from hacking into the devices of defence ministry officials.

"We've developed a system to restrict the core functions of smartphones because of concerns that our work could be leaked through them," he said.

For now, the app only works in the ministry compound. Officials said all South Korean soldiers would be ordered to install it later.

The ministry promised to upgrade the app after an operational flaw emerged.

Users of Samsung's Galaxy and other Android phones can receive and make calls and text messages, but iPhone users can only receive calls and text messages.

Yonhap quoted an unnamed air force lieutenant colonel as saying: "Even if I bring my iPhone 4 that passed the security review, I can only receive calls and text messages. What can I do with the dumb phone?"

About 70 percent of South Korea's 50 million people have smartphones -- the world's highest penetration rate.