SEOUL (AFP) - South Korean security authorities are probing Swedish defense firm Saab, maker of the Gripen fighter jet, amid allegations of bribery to secure secret information.

The defence ministry said security officials last month raided the Seoul branch of Saab and the Security Management Institute, a private organisation with access to key defence information.

"The raid, which was to secure evidence, followed allegations of bribery," a ministry spokesman told AFP, without disclosing details.

The Swedish company is suspected of bribing the institute to obtain information regarding a military project to develop new fighter jets, Yonhap news agency said.

Saab has been interested in the project, Yonhap said, adding its potential competitors include US firms Boeing and Lockheed Martin.

Yonhap quoted Kim Jong-Tae, commander of the Defence Security Command, as saying security authorities were questioning six people.

"The investigation should end at the end of October," Kim was quoted as saying.

Investigators suspect the institute has presented reports on the fighter project to parliament in favour of Saab, Yonhap said.

South Korea hopes to secure more than 100 new fighters by 2020 to better counter threats from its neighbours. It has purchased 40 F-15Ks from Boeing and plans to buy 21 more by 2012.