Australia says a Chinese fighter jet has released flares "in close proximity to" an Australian air force maritime patrol aircraft over the South China Sea. It says both the aircraft and its crew were unharmed.

Australia's defense department made the announcement in a statement on Thursday.

It said the incident occurred on Tuesday, when the Australian aircraft was conducting routine surveillance over the waters.

The department described the Chinese maneuver as "unsafe and unprofessional." It said it "has expressed its concerns to the Chinese government."

Chinese foreign ministry spokesperson Guo Jiakun said at a news conference on Thursday that the Australian plane violated China's sovereignty by deliberately intruding into its airspace over the South China Sea.

Guo said, "The Chinese side took legitimate, lawful, professional and restrained measures to expel" the Australian plane. He added, "China has lodged serious protests with Australia."

The Australian defense department also announced that a Chinese navy task group is operating to the northeast of Australia. It said the group consisted of a frigate, a cruiser and a replenishment vessel.

The department released two photographs it says show the Chinese frigate.

Australian defense minister Richard Marles noted that he has ordered the deployment of navy and air force assets to make sure that Australian forces are "shadowing" the Chinese group and "have a clear understanding of what's going on."