MARINE conservation activists Sea Shepherd have had a brush with the Chinese navy as they pursue an alleged illegal driftnet fishing vessel through the South China Sea.

The MV Steve Irwin began the chase of the Chinese flagged Fu Yuan Yu 76 on Saturday after observing it as part of a small fleet of six vessels illegally driftnet fishing in the Indian Ocean..

The Sea Shepherd vessel singled out the Fu Yuan, chasing it through the narrow Malacca Straits, past Singapore and into the contested South China Sea.

You know you're in the South China Sea when this happens. #OpDriftnet progresses closer to the China. Stay tuned. pic.twitter.com/yXAJ6r9xIH — Sid Chakravarty (@OceanBanter) March 23, 2016

“The Fu Yuan Yu 076 has switched off its Automatic Identification System (AIS),” a Sea Shepherd statement reads. “Sea Shepherd’s Flagship, The MV Steve Irwin, remains on the tail of the illegal vessel ensuring that its location is relayed to the relevant authorities across the world, including authorities in China.”

The Sea Shepherd statement provided photographic evidence of what it says was the ship destroying its illegal driftnet equipment, and concealing its identity.

The Steve Irwin followed the Fu Yuan into China’s Exclusive Economic Zone on Tuesday. Yesterday, China’s navy made its presence felt.

Sea Shepherd has posted video purporting to show the Steve Irwin’s Sid Chakravarty informing two nearby People’s Liberation Army Navy ships of the Fu Yuan’s offences.

So far, the Chinese ships have not responded. Nor have they attempted to intervene beyond observing proceedings.

The chase comes at a time of heightened tension over illegal fishing in and around the South China Sea.

At the weekend Indonesian fisheries police boarded a Chinese fishing vessel 4.3km off the coast of Natuna Island, part of Jakarta’s established Exclusive Economic Zone.

Two Chinese Coast Guard vessels then intervened, ramming the 300 ton Kway Fey 10078 while it was under tow. Chinese Coast Guard personnel then commandeered the seized vessel from its Indonesian fisheries police crew, guiding it back out of territorial waters.

China has since issued a complaint to Indonesia, demanding the fishermen be released on the basis they were operating in ‘traditional fishing grounds’.

Last week, a Chinese fishing vessel was sunk by the Argentine navy after being intercepted while fishing illegally in its territorial waters. All 32 crew were rescued by the navy or other nearby Chinese vessels.