Indonesia's Air Force says a private jet that violated Indonesian airspace yesterday was en route to the G20 Leaders' Summit in Brisbane.

Two Indonesian air force Sukhoi fighter jets were scrambled to chase the plane, which was travelling through its airspace without clearance.

Indonesian air force spokesman Hadi Tjahjanto said the Gulfstream jet was en route from Saudi Arabia to Brisbane for the G20 meeting next week.

Brigadier-General Tjahjanto said six crew and four passengers were onboard the private jet when it was forced to land in Kupang, West Timor.

They were questioned and released late last night.

Two weeks ago, an Australian private jet heading to the Philippines was forced to land in Sulawesi when it violated Indonesian airspace.

Two Australian men were later fined nearly $6,000 and then released.

Indonesia's military head, General Moeldoko, said the country's airspace restrictions should be more heavily controlled and enforced.