The Government Flying Service (GFS) said on Saturday it had deployed rescuers to help more than two dozen sailors stranded at sea after their vessel snapped in half near the eye of Typhoon Chaba.

As of 3:30pm on Saturday, at least three people had been rescued, according to the service. It said that they told of holding on for their lives to the vessel's railings before they were lifted to safety, and that they suspected others had been swept away by waves.

In a social media post, GFS said it had been notified of the incident at about 7:25am.

It said the vessel was located in waters about 300 kilometres off the southwest of Hong Kong when it broke in half. Around 30 people onboard had abandoned the vessel.

Videos taken by the GFS show what appears to be half of the vessel having tilted, and rescuers lifting survivors to safety in harsh weather conditions which have clearly hampered efforts.

"As the incident happened near the eye of Typhoon Chaba, adverse weather has made rescue efforts very difficult," the service wrote in its post.

It said it has deployed a fixed-wing aircraft and two helicopters for the mission.

It added that the mainland's Nanhai Rescue Bureau had also sent a ship to assist.