Chinese maritime militia vessels are believed responsible for a series of laser attacks on Australian pilots during a recent voyage through the hotly contested South China Sea.

Key points: Defence sources have confirmed helicopters were targeted with lasers during night flights

Defence sources have confirmed helicopters were targeted with lasers during night flights It comes after Chinese warships closely followed the Australian Task Group

It comes after Chinese warships closely followed the Australian Task Group Beijing maintains a robust maritime militia in the disputed South China Sea

Defence sources have confirmed helicopters were targeted during night flights, forcing the pilots to temporarily return to their ship for medical check-ups.

The incidents occurred as Australian warships were completing Indo-Pacific Endeavour 2019, an ADF regional engagement mission that wrapped up this week.

This week the ABC revealed the Australian Task Group had been closely followed earlier this month by Chinese warships as they travelled between Vietnam and Singapore through the South China Sea.

Australian military officials believe the laser attacks on the Navy helicopters came from fishing boats, but it has not yet been formally confirmed if the vessels were Chinese flagged.

A Royal Australian Navy MRH90 Taipan multi-role helicopter. ( ABIS: Tom Gibson )

Beijing maintains a robust maritime militia in the South China Sea, composed of fishing vessels equipped to carry out missions just short of combat.

The Australian Defence Department is yet to comment publicly, but similar incidents involving lasers and the Chinese military have also been reported as far away as Djibouti, where the US and China have bases.

Last year, the US complained to China after lasers were directed at aircraft in the Horn of Africa nation, resulting in minor injuries to two American pilots.

Following reports last year of a series of laser attacks on US aircraft in the Pacific, the Australian Defence Department publicly condemned the practice.

"The Australian Government would view reports of military aircraft being targeted by lasers as an unwelcome and potentially dangerous development," a Defence spokesperson told the ABC in July 2018.

Beijing has routinely denied any involvement in laser attacks on US aircraft, but this is the first publicised incident to have targeted Australian personnel.