Hong Kong(CNN) Australian military helicopters were targeted with lasers during operations in the South China Sea this month.

"Some helicopter pilots had lasers pointed at them from passing fishing vessels," Euan Graham of the Australian Strategic Policy Institute wrote on The Strategist blog, who was aboard the warship from which the aircraft were operating.

Graham told CNN he did not witness the incidents, but Australian pilots told him they were targeted multiple times by commercial lasers during South China Sea missions.

Graham was aboard HMAS Canberra, a helicopter landing dock and flagship of the Royal Australian Navy, as it operated in the South China Sea and Indian Ocean on a three-month mission that ended this week.

Australian forces across the region have noticed the increased use of lasers, an Australian Defense Department spokesperson said in a statement.

"The reason for vessels using the lasers is unknown, but it may be to draw attention to their presence in congested waterways," the statement said.

At sea, fishermen are known to use lasers to warn off other vessels that may be getting too close to them.

"That makes sense for collision of vessels, but obviously there is no direct threat from aircraft to vessels in the South China Sea," Graham said. "The maritime militia is, I think, not beyond argument as a tactic which is employed deliberately."

Graham said that the Canberra and other Australian ships operating with it were shadowed almost continuously by Chinese warships while in the South China Sea, even though they did not approach any of the islands and reefs occupied by the Chinese military.

Radio communications between the Australian and Chinese forces were courteous, Graham said.

CNN reached out to the Chinese Ministry of Defense but did not immediately hear back.

Military militia?

China has claimed almost the entire 1.3 million square mile South China Sea as its sovereign territory. In recent years it has aggressively asserted its stake in the face of conflicting claims from several Southeast Asian nations.

As part of that, Beijing operates a maritime militia in this region, a force of fishing vessels essentially deputized to the Chinese navy.

In Hainan, a South China Sea island, local fishermen assisted in more than 250 law enforcement operations at sea over a three-year period ending in 2016, according to a report from China Military Online.

"It's no secret that the broader thrust of China's approach in the South China Sea is to try to make life difficult for foreign aircraft and warships there," Graham said.

US military officials told CNN last year that there were at least 20 suspected Chinese laser incidents in the eastern Pacific from September 2017 to June 2018.

And in May 2018, US military officials said Chinese personnel at the country's military base in Djibouti were using lasers to interfere with US military aircraft at a nearby American base.

Pilots targeted by laser attacks have reported disorienting flashes, pain, spasms and spots in their vision. The dazzle effect can trigger temporary blindness, with "catastrophic" consequences, according to John Marshall, a professor at University College of London's Institute of Ophthalmology.

"The inappropriate use of lasers would pose a potential safety risk to all those operating in the region," the Australian Department of Defense statement said.

No injuries were into Australian Navy pilots were reported from the recent incidents, the statement said.