Malaysia’s maritime agency said it has detained a Chinese-registered vessel on suspicion of looting two Second World War-era British shipwrecks in the South China Sea.

The agency said it had found a cannon shell believed to be from the Second World War on board the bulk carrier ship.

Malaysian media reported that illegal salvage operators are believed to have targeted the HMS Repulse and the HMS Prince of Wales, which were sunk in 1941 by Japanese torpedoes just days after the attack on Pearl Harbour.

A total of 842 sailors perished, and the shipwrecks off the coast of central Pahang state are designated as war graves.

Fishermen and divers alerted authorities after spotting a foreign vessel near the area last month.

The agency said it detained the vessel registered in Fuzhou, China, on Sunday for anchoring without a permit off southern Johor state.

It said there were 32 crew members aboard, including 21 from China, 10 from Bangladesh and one from Malaysia.

The agency said officials from the National Heritage Department and others will work together to identify the cannon shell.

The UK’s National Museum of the Royal Navy last week said it was “distressed and concerned at the apparent vandalism for personal profit”.

The maritime agency said it believed the rusty cannon shell was linked to the police seizure of dozens of unexploded artillery and other relics at a private scrapyard in Johor.

The New Straits Times newspaper reported that the munitions were believed to be from the warships and that police conducted an on-site controlled explosion of the weapons.

Pictures and a video released by the agency showed a barge carrier with a large crane and heaps of rusty metal on board.

Known as pre-war steel, the material from the two warships is valuable and could be smelted for use in manufacturing of some scientific and medical equipment.

It is not the first time that the two shipwrecks have been targeted.

The New Straits Times reported that foreign treasure hunters used homemade explosives in 2015 to detonate the heavy steel plates on the ships for easy pickings.

Other media said authorities detained a Vietnamese vessel involved in the looting of the wreckage at the time.