Indonesia refused to take the blame Thursday for the disappearance of at least six British and Dutch World War II shipwrecks -- considered war graves -- that investigators believe could have been salvaged for scrap.

Former colonial ruler The Netherlands has launched a probe into how three Dutch navy ships seemingly vanished from the bed of the Java Sea, while Britain has urged Indonesia to investigate what has happened to three of its vessels.

It is believed the military wrecks -- lost in 1942 during the Battle of the Java Sea -- were removed by illegal scavengers looking for scrap metal, an effort that could have taken years.

More than 900 Dutch and 250 Indo-Dutch sailors died during the battle in which the Allied navies suffered a disastrous defeat by the Imperial Japanese Navy.

Indonesian authorities have sought to distance themselves from the mystery, saying they could not be expected to protect the sites without assistance.

"The Dutch government cannot blame the Indonesian government because they never asked us to protect those ships," said Bambang Budi Utomo, head of the National Archeological Centre under the Ministry of Education and Culture.

"As there was no agreement or announcement, when the ships go missing, it is not our responsibility."

- Looting took years -

Amateur divers in 2002 discovered the long-lost wrecks of three Dutch ships, 60 years after they sank while in action against Japanese forces.

But an international expedition that sailed to the wreck site ahead of next year's 75th anniversary of the battle was shocked to discover the wrecks had vanished.

Britain expressed its distress at the disappearance of its own warships and asked Indonesia to "take appropriate action" to protect the sites from further disturbance.

But Utomo said Indonesia did not have the resources to maintain a constant patrol across the vast archipelago, adding the wrecks didn't disappear overnight.

"The looting must have been going on for years for such a huge ship to disappear," he said.

"Looters are fearless," he added, saying divers risked death and injury sucking air through pipes to retrieve valuable scrap and antiquities by hand.

Scavengers are known to target Indonesia's relic-rich seas, experts say, where countless vessels have gone to a watery grave over centuries of trade, colonial conquest and war.  

Australia has been working closely with Indonesia to protect HMAS Perth -- which sunk off Java in World War II, claiming hundreds of lives -- after discovering in 2013 the warship was being plundered for brass.

A spokesman for the Indonesian navy said the missing ships should not have been disturbed as they were war graves.

"However, the Indonesian navy cannot monitor all areas all the time," spokesman Gig Jonias Mozes Sipasulta told AFP.

"If they ask why the ships are missing, I'm going to ask them back, why didn't they guard the ships? They should have been more proactive."

Naval warships and war graves are protected under international law that makes the desecration of such shipwrecks illegal.

Source: AFP