HANOI - Vietnamese transport ministry has ordered its aviation sector to tighten security after a Malaysian jet went missing near the country.

Dinh Viet Thang, deputy chief of the Civil Aviation Administration of Vietnam (CAAV), told Dan Tri (Knowledge for People) online newspaper on Monday that Vietnam is now on the first level of a three-level security alert system.

Thang said an initial warning is necessary for improving the national aviation security, as a Malaysian airplane disappeared near Vietnam, reported Thanhnien (Young People) online Monday.

Accordingly, security was tightened in and around the country's largest airport Tan Son Nhat in southern Ho Chi Minh City and Noi Bai International Airport in capital Hanoi.

Passengers are randomly subjected to intensive checks, before boarding a plane.

Flight MH370, carrying 12 crew members and 227 passengers, including 154 Chinese, operated by Malaysia Airlines' Boeing 777-200 left Kuala Lumpur International Airport for Beijing lost contact with air traffic control on Saturday when it was flying over the Ho Chi Minh air traffic control area in south Vietnam.

Interpol on Sunday confirmed that at least two stolen passports were used by unidentified passengers on the plane, adding that the agency is investigating more suspicious passports involved.

On Saturday, Italian and Austrian authorities confirmed that passports of Christian Kozel and Luigi Maraldi, whose names were listed in the MH370 manifest, had both been stolen in Thailand.