Two Chinese trawlers seized in Australian waters have been taken to the northern city of Darwin and may be destroyed if found guilty of illegal action, a Australian government official said on Sunday.

The vessels, De Yuan Yu 001 and De Yuan Yu 002, carrying 27 crew, were intercepted by an Australian naval vessel inside the Australian fishing zone northwest of the Wessels islands early on Thursday.

A spokesman for Australia's Minister for Fisheries, Forestry and Conservation, Eric Abetz, told Reuters on Sunday that the vessels had been taken to Australia's northern city of Darwin.

"What happens to them depends on the investigation. Normally they would be destroyed if found guilty," he said.

Australian Fisheries Management Authority officers will investigate whether charges will be laid.

Initial investigations by Australian Fisheries Management found about 4,000 kg of reef fish on board the De Yuan Yu 001, and 3,000 kg on board the De Yuan Yu 002, the Australian government has said.

Australian officials said on the weekend that a new trend may be emerging in illegal poaching in Australian waters, which so far has been dominated by Indonesian fishermen, often in ramshackle vessels.

"It is of concern because these (the Chinese) vessels are quite capable of catching a lot of fish," a spokesman for Australian Fisheries Management told Australian Broadcasting Corp television on Saturday night.

The seized Chinese vessels each weigh about 123 tonnes and are 31 metres in length.

Thirteen crew were found on board one vessel and 14 on the other. All are People's Republic of China nationals, the Australian government has said.

The Chinese embassy in Canberra has told China's Xinhua news service that the two vessels were on their way to a nearby refuelling vessel, and said they were in Australian waters because of current and wind factors.

In another development, an abandoned mystery ship was found floating off the coast of northern Australia in the Gulf of Carpentaria on Saturday.

Australian customs officers boarded the 80-metre long vessel, named Jian Seng. Its nationality and port of origin is unknown, an Australian customs spokesman said.

The ship was trailing a broken tow rope from its bow and may have been abandoned because it was inoperable, he said.

The Jiang Seng is the second ghost ship to be found in Australian waters in recent times. The Taiwanese fishing vessel High Aim 6 was found drifting off the northwestern coast of Western Australia in 2003, and was sunk off the western township of Broome.