NEW DELHI: Taking cautious approach, the ministry of defence on Wednesday ordered a probe into the sensational leak of highly classified documents by an Australian media on the capabilities of six under construction advanced submarine for the India Navy in collaboration with a French defence giant.

More than 22,000 pages of the secret stealth capability of the Indian navy’s Scorpene submarines being built at Mazagon dock in Mumbai at a cost of USD 3.5 billion by French shipbuilder DCNS, went public when an Australian newspaper, "The Australian", put the details on the website.

'Marked "Restricted Scorpene India", the DCNS documents­ detail the most sensitive combat capabilities of India’s submarine fleet and would provide an intelligence bonanza if obtained by India’s strategic rivals, such as Pakistan or China, Australian media report says.

Trying to down play the issue, the MoD sources say that “leaked documents are different what we have.” However, the Navy in a statement clarified that "It appears that the source of leak is from overseas and not in India." Moreover, navy stressed that induction of the first of six Scorpene submarine will happen at its scheduled programme by the month of October-November later this year. And rest five will be delivered subsequently with every nine months gap thereafter.

Defence minister Manohar Parrikar, who claims to have learnt about the lead at midnight, instructed Navy Chief Admiral Sunil Lamba to go into the ‘entire issue.’ "What I understand is there is a hacking. So we will find out all this," Parrikar said on the sidelines of an event in Delhi. The Defence Minister said he does not suspect the leak to be 100 per cent since a lot of final integration lies with India. He said a clear picture will emerge in a couple of days.

Sources also indicate that it (leak) could be a result of corporate war between the defence manufacturing firms as DCNS has won the Australian submarine contract two months back only to built 12 submarine deal worth $38 million for Australian navy after defeating Japanese and German firms in the bid.

According to naval sources, the leak of data "was a matter of serious concern" but added that the document was dated and the Indian submarine had undergone "many changes" from the initial design the details of which have been leaked.

The details leaked included what frequencies the submarines gather intelligence at, what levels of noise they make at various speeds and their diving depths, range and endurance — all sensitive information that is highly classified, the Australian said.

The data tells the submarine crew where on the boat they can speak safely to avoid detection by the enemy. It also discloses magnetic, electromagnetic and infra-red data as well as the specifications of the submarine’s torpedo launch system and the combat system, the newspaper said. It details the speed and conditions needed for using the periscope, the noise specifications of the propeller and the radiated noise levels that occur when the submarine surfaces.

The data, accessed by the paper, includes 4457 pages on the submarine's underwater sensors, 4209 pages on its above-water sensors, 4301 pages on its combat management system, 493 pages on its torpedo launch system and specifications, 6841 pages on the sub's communications system and 2138 on its navigation systems.

In a statement, the Navy said, "A case of suspected leak of documents related to Scorpene submarines has been reported by a foreign media house.

"The available information is being examined at Integrated Headquarters, Ministry of Defence (Navy) and an analysis is being carried out by the concerned specialists. "It appears that the source of leak is from overseas and not in India."

Later in the day, Parrikar also met the naval top brass to discuss the leak episode.

Congress leader A K Antony, a former Defence Minister, said the leak is a matter of "very very serious concern" to the country.

"It affects the security of the country. Government must immediately order a high level enquiry, find out the truth after that we can consider future course of action. Don't waste time immediately find out the truth," he said.

In the evening, DCNS issued an statement from its headquarters in Paris. "We have been made aware of articles published in the Australian press related to the leakage of sensitive data about Indian Scorpene. This serious matter is thoroughly being investigated by the proper French national authorities for Defense Security. This investigation will determine the exact nature of the leaked documents, the potential damages to DCNS customers as well as the responsibilities for this leakage".

The manufacturer said the leak could be the work of competitors who it beat for the large Australian contract.

"The competition is more and more hard and all means can be used in this context," said a DCNS spokeswoman quoted by news agency . "It's part of the tools in economic war," she said.

Indian in October 2005 signed contract to built six scorpene submarines with DCNS with cost of $ 3.5 million and first submarine scheduled to be delivered by October-November later this year.

The leak has cast a shadow over future defence agreements with France and may also have a bearing on Indo-French diplomatic relations. The multi-billion-dollar deal for 36 Rafale fighter jets with the French firm Dassault and the DRDO’s short-range surface-to-air missile project with MBDA are among the deals that are likely to be affected. India and France have been working hard to finalise the Rafale warplane contract with an approximate cost of 7. 8 billion euros. The DRDO’s ‘Maitri’ project to co-develop short-range missiles with the French company MBDA is also in the pipeline and was discussed in the recently concluded meeting of the ministry’s top acquisition body.

Australian Prime Minister Malcolm Turnbull reacted on leak by saying in Canberra that it was "of concern", the Scorpene was a different model to the subs Australia is buying. Australian media reported that the data was thought to have been removed from France in 2011 by a former French naval officer who at the time was a subcontractor for DCNS. The data is believed to have passed through firms in Southeast Asia before eventually being mailed to a company in Australia, the newspaper said.